Oxethazaine inhibits hepatitis B virus capsid assembly by blocking the cytosolic calcium-signalling pathway

The synergistic antibacterial activity and mechanism of colistin-oxethazaine combination against gram-negative pathogens

Background

The rapid spread of bacteria with plasmid-mediated resistance to antibiotics poses a serious threat to public health. The search for potential compounds that can increase the antibacterial activity of existing antibiotics is a promising strategy for addressing this issue.

Methods

Synergistic activity of the FDA-approved agent oxethazine combined with colistin was investigated in vitro using checkerboard assays and time-kill curves. The synergistic mechanisms of their combination of oxethazine and colistin was explored by fluorescent dye, scanning electron microscopy (SEM) and LC-MS/MS. The synergistic efficacy was evaluated in vivo by the Galleria mellonella and mouse sepsis models.

Results

In this study, we found that oxethazine could effectively enhance the antibacterial activity of colistin against both mcr-positive and -negative pathogens, and mechanistic assays revealed that oxethazine could improve the ability of colistin to destruct bacterial outer membrane and cytoplasmic membrane permeability. In addition, their combination triggered the accumulation of reactive oxygen species causing additional damage to the membrane structure resulting in cell death. Furthermore, oxethazine significantly enhanced the therapeutic efficacy of colistin in two animal models.

Conclusion

These results suggested that oxethazine, as a promising antibiotic adjuvant, can effectively enhance colistin activity, providing a potential strategy for treating multidrug-resistant bacteria.

Oxethazaine inhibits esophageal squamous cell carcinoma proliferation and metastasis by targeting aurora kinase A

Esophageal squamous cell carcinoma (ESCC), a malignant neoplasm with high incidence, is a severe global public health threat. The current modalities used for treating ESCC include surgery, chemotherapy, and radiotherapy. Although ESCC management and treatment strategies have improved over the last decade, the overall 5-year survival rate remains <20%. Therefore, the identification of novel therapeutic strategies that can increase ESCC patient survival rates is urgently needed. Oxethazaine, an amino-amide anesthetic agent, is mainly prescribed in combination with antacids to relieve esophagitis, dyspepsia, and other gastric disorders. In the present study, we found that oxethazaine inhibited the proliferation and migration of esophageal cancer cells. According to the results of in vitro screening and binding assays, oxethazaine binds directly to AURKA, suppresses AURKA activity, and inhibits the downstream effectors of AURKA. Notably, we found that oxethazaine suppressed tumor growth in three patient-derived esophageal xenograft mouse models and tumor metastasis in vivo. Our findings suggest that oxethazaine can inhibit ESCC proliferation and metastasis in vitro and in vivo by targeting AURKA.

Calcium signaling in hepatitis B virus infection and its potential as a therapeutic target

As a ubiquitous second messenger, calcium (Ca2+) can interact with numerous cellular proteins to regulate multiple physiological processes and participate in a variety of diseases, including hepatitis B virus (HBV) infection, which is a major cause of hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. In recent years, several studies have demonstrated that depends on the distinct Ca2+ channels on the plasma membrane, endoplasmic reticulum, as well as mitochondria, HBV can elevate cytosolic Ca2+ levels. Moreover, within HBV-infected cells, the activation of intracellular Ca2+ signaling contributes to viral replication via multiple molecular mechanisms. Besides, the available evidence indicates that targeting Ca2+ signaling by suitable pharmaceuticals is a potent approach for the treatment of HBV infection. In the present review, we summarized the molecular mechanisms related to the elevation of Ca2+ signaling induced by HBV to modulate viral propagation and the recent advances in Ca2+ signaling as a potential therapeutic target for HBV infection. Video Abstract.

Endoplasmic reticulum & mitochondrial calcium homeostasis: The interplay with viruses

Calcium ions (Ca²⁺) act as secondary messengers in a plethora of cellular processes and play crucial role in cellular organelle function and homeostasis. The average resting concentration of Ca²⁺ is nearly 100 nM and in certain cells it can reach up to 1 µM. The high range of Ca²⁺ concentration across the plasma membrane and intracellular Ca²⁺ stores demands a well-coordinated maintenance of free Ca²⁺ via influx, efflux, buffering and storage. Endoplasmic Reticulum (ER) and Mitochondria depend on Ca²⁺ for their function and also serve as major players in intracellular Ca²⁺ homeostasis. The ER-mitochondria interplay helps in orchestrating cellular calcium homeostasis to avoid any detrimental effect resulting from Ca²⁺ overload or depletion. Since Ca²⁺ plays a central role in many biological processes it is an essential component of the virus-host interactions. The large gradient across membranes enable the viruses to easily modulate this buffered environment to meet their needs. Viruses exploit Ca²⁺ signaling to establish productive infection and evade the host immune defense. In this review we will detail the interplay between the viruses and cellular & ER-mitochondrial calcium signaling and the significance of these events on viral life cycle and disease pathogenesis.

Chloroquine to fight COVID-19: A consideration of mechanisms and adverse effects?

The COVID-19 outbreak emerged in December 2019 and has rapidly become a global pandemic. A great deal of effort has been made to find effective drugs against this disease. Chloroquine (CQ) and hydroxychloroquine (HCQ) were widely adopted in treating COVID-19, but the results were contradictive. CQ/HCQ have been used to prevent and treat malaria and are efficacious anti-inflammatory agents in rheumatoid arthritis and systemic lupus erythematosus. These drugs have potential broad-spectrum antiviral properties, but the underlying mechanisms are speculative. In this review, we re-evaluated the treatment outcomes and current hypothesis for the working mechanisms of CQ/HCQ as COVID-19 therapy with a special focus on disruption of Ca2+ signaling. In so doing, we attempt to show how the different hypotheses for CQ/HCQ action on coronavirus may interact and reinforce each other. The potential toxicity is also noted due to its action on Ca2+ and hyperpolarization-activated cyclic nucleotide-gated channels in cardiac myocytes and neuronal cells. We propose that intracellular calcium homeostasis is an alternative mechanism for CQ/HCQ pharmacology, which should be considered when evaluating the risks and benefits of therapy in these patients and other perspective applications.

Pemetrexed inhibits Kaposi's sarcoma-associated herpesvirus replication through blocking dTMP synthesis

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. In immunocompromised patients, KSHV infection is capable of causing severe and fatal diseases. Current antiviral treatments for KSHV infections consist mostly of nucleoside analogs, all of which target viral polymerases and are associated with adverse effects and drug resistance. By screening an FDA-approved drug library, we identified pemetrexed as a potent anti-KSHV agent, with an IC₅₀ of 90 nM. Characterization of the antiviral properties of pemetrexed revealed that it interferes with the lytic replication of viral DNA, resulting in the reduction of infectious virions. The antiviral effect of pemetrexed depends on the dTMP synthesis pathway that requires the folate-dependent enzymes. Besides, pemetrexed shows a broad spectrum of anti-herpes virus activity. Thus, our findings suggest that pemetrexed inhibits the lytic replication of KSHV DNA by blocking dTMP synthesis. Pemetrexed has the potential to be utilized as an anti-KSHV agent.

Evans Blue Inhibits HBV Replication Through a Dual Antiviral Mechanism by Targeting Virus Binding and Capsid Assembly

Chronic hepatitis B (CHB) is a global health problem caused by human hepatitis B virus (HBV). Current treatment with interferons and nucleos(t)ide analogs (NAs) can cause population tolerance and drug resistance. Therefore, new antiviral drugs, especially those targeting host factors, are urgently needed. Here, we identified Evans blue as a new HBV inhibitor by screening an FDA drug library using Huh7D^hNTCP cells and confirmed the antiviral activity in primary human hepatocytes and human sodium taurocholate cotransporting polypeptide (hNTCP)-transfected porcine primary hepatocytes. Our efficacy study showed that Evans blue has an IC₅₀ of 2 μM against HBV infection in Huh7D^hNTCP cells, and no apparent toxicity at up to 1000 μM. The IC₅₀ of Evans blue against HBV in primary human hepatocytes was approximately 5 μM. Mechanism studies revealed that Evans blue has a dual anti-HBV effect. It inhibits both the binding of viral preS1 to host cells through the host factor NTCP and the virus capsid assembly by targeting the host factor BK channel. The K_D of the direct interaction between Evans blue and NTCP is 8.82E-8 M. Evans blue can suppress capsid assembly at micromolar concentrations by reducing the cytosolic calcium ion concentration. Since the antiviral effects on HBV binding and assembly are both achieved through targeting host factors, Evans blue inhibits the infection of nucleos(t)ide analog drug-resistant HBV strains in Huh7D^hNTCP cells. Taken together, our results suggest that Evans blue may be a promising anti-HBV drug candidate in the classes of both entry and assembly inhibitors.

Role of Protein Charge Density on Hepatitis B Virus Capsid Formation

The role of electrostatic interactions in the viral capsid assembly process was studied by comparing the assembly process of a truncated hepatitis B virus capsid protein Cp149 with its mutant protein D2N/D4N, which has the same conformational structure but four fewer charges per dimer. The capsid protein self-assembly was investigated under a wide range of protein surface charge densities by changing the protein concentration, buffer pH, and solution ionic strength. Lowering the protein charge density favored the capsid formation. However, lowering charge beyond a certain point resulted in capsid aggregation and precipitation. Interestingly, both the wild-type and D2N/D4N mutant displayed identical assembly profiles when their charge densities matched each other. These results indicated that the charge density was optimized by nature to ensure an efficient and effective capsid proliferation under the physiological pH and ionic strength.

Complexation of oxethazaine with 2-hydroxypropyl-β-cyclodextrin: increased drug solubility, decreased cytotoxicity and analgesia at inflamed tissues

Objectives

Oxethazaine (OXZ) is one of the few local anaesthetics that provides analgesia at low pH, but presents poor solubility, cytotoxicity and no parenteral formulations. To address these issues, we aimed to prepare OXZ host-guest inclusion complex with hydroxypropyl-beta-cyclodextrin (HP-β-CD).

Methods

The inclusion complex was formed by co-solubilization, followed by a job plot analysis to determine stoichiometry of complexation and dialysis equilibrium analysis (based on UV/VIS absorption and fluorescence profiles of OXZ). Complex formation was confirmed by phase-solubility data, X-ray, Scanning Electron Microscopy and DOSY-1H-NMR experiments. In vitro cytotoxicity was analysed by MTT test in 3T3 fibroblasts. In vivo analgesia was tested by Von Frey test (inflammatory wounds – rats).

Key findings

Oxethazaine complexed (1 : 1 molar ratio) with HP-β-CD, as indicated by loss of OZX crystalline structure (X-ray) and strong host: guest interaction (NMR, K = 198/m), besides increased solubility. In vitro cell survival improved with the complex (IC50 OXZ = 28.9 μm, OXZ : HP-β-CD = 57.8 μm). In addition, the complex (0.1% OXZ) promoted in vivo analgesia for the same time that 2% lidocaine/epinephrine did.

Conclusion

Our results show that complexation improved physicochemical and biological properties of OXZ, allowing its application to inflamed tissues by parenteral routes.