iPSC Neuronal Assay Identifies Amaryllidaceae Pharmacophore with Multiple Effects against Herpesvirus Infections

Identification of potential targets against SARS-CoV-2 of antiviral drugs based on photoaffinity probes

Facing the sudden outbreak of coronavirus disease 2019 (COVID-19), it is extremely urgent to develop effective antiviral drugs against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Drug repurposing is a promising strategy for the treatment of COVID-19. To identify the precise target protein of marketed medicines, we initiate a chemical biological program to identify precise target of potential antivirus drugs. In this study, two types of recombinant human coronavirus SARS-CoV-2 RdRp protein capturing probes with various photoaffinity labeling units were designed and synthesized based on the structure of FDA-approved drugs stavudine, remdesivir, acyclovir, and aladenosine. Fortunately, it was found that one novel photoaffinity probe, RD-1, could diaplayed good affinity with SARS-CoV-2 RdRp around the residue ARG_553. In addition, RD-1 probe also exhibited potent inhibitory activity against 3CLpro protease. Taken together, our findings will elucidate the structural basis for the efficacy of marketed drugs, and explore a rapid and efficient strategy of drug repurposing based on the identification of new targets. Moreover, these results could also provide a scientific basis for the clinical application of marketed drugs.

Truncated ring-A amaryllidaceae alkaloid modulates the host cell integrated stress response, exhibiting antiviral activity to HSV-1 and SARSCoV-2

The total synthesis of four novel mono-methoxy and hydroxyl substituted ring-A dihydronarciclasine derivatives enabled identification of the 7-hydroxyl derivative as a potent and selective antiviral agent targeting SARSCoV-2 and HSV-1. The concentration of this small molecule that inhibited HSV-1 infection by 50% (IC50), determined by using induced pluripotent stem cells (iPCS)-derived brain organ organoids generated from two iPCS lines, was estimated to be 0.504 µM and 0.209 µM. No significant reduction in organoid viability was observed at concentrations up to 50 mM. Genomic expression analyses revealed a significant effect on host-cell innate immunity, revealing activation of the integrated stress response via PERK kinase upregulation, phosphorylation of eukaryotic initiation factor 2α (eIF2α) and type I IFN, as factors potentiating multiple host-defense mechanisms against viral infection. Following infection of mouse eyes with HSV-1, treatment with the compound dramatically reduced HSV-1 shedding in vivo.

Antiviral alkaloid principles of the plant family Amaryllidaceae

BACKGROUND

Viral-borne diseases are amongst the oldest diseases known to mankind. They are responsible for some of the most ravaging effects wrought on human health and well-being. The use of plants against these ailments is entrenched in both traditional and secular medicine around the globe. Their natural abundance and chemical diversity have also boosted their appeal in drug discovery.

AIM

The plant family Amaryllidaceae is distinguished for its alkaloid principles, some of which are of considerable interest in the clinical arena. This account is the outcome of a literature review undertaken to establish the applicability of these substances as antiviral agents.

METHODS

The survey utilized the search engines Google Scholar, PubMed, SciFinder, Scopus and Web of Science engaging the word 'antiviral' in conjunction with 'Amaryllidaceae' and 'Amaryllidaceae alkaloid'. The search returned over five hundred hits, of which around eighty were of relevance to the theme of the text.

RESULTS

Over eighty isoquinoline alkaloids have been screened against nearly fifty pathogens from fourteen viral families, the majority of which were RNA viruses. Potent activities were reported in some instances, such as that of trans-dihydronarciclasine against Yellow fever virus (IC₅₀ 0.003 μg/ml), with minimal effects being manifested on host cells. There were also promising results obtained from in vivo studies, in most cases without lethal effects on test subjects. Structure-activity relationship studies afforded useful insight to the antiviral pharmacophore, with the phenanthridone alkaloid nucleus shown to be the most enabling. Although the mechanistic basis to these activities pertained mostly to inhibition of DNA, RNA and protein synthesis, evidence was also forthcoming about the inhibitory action of some of the alkaloids against viral neuraminidase, protease and reverse transcriptase. In silico methods of analysis have offered further perspectives of how some of the alkaloids interact at the active sites of their targets.

CONCLUSION

The Amaryllidaceae offers a viable platform for plant-based antiviral drug discovery. Its cause is strengthened not only by its wide proliferation and exploitation of its members in alternative forms of medicine, but also by its rich chemical diversity which has already spawned useful antiviral drug leads.

Medicinal plants and natural compounds against acyclovir-resistant HSV infections

Herpes simplex virus (HSV), an alphaherpesvirus, is highly prevalent in the human population and is known to cause oral and genital herpes and various complications. Represented by acyclovir (ACV), nucleoside analogs have been the main clinical treatment against HSV infection thus far. However, due to prolonged and excessive use, HSV has developed ACV-resistant strains. Therefore, effective treatment against ACV-resistant HSV strains is urgently needed. In this review, we summarized the plant extracts and natural compounds that inhibited ACV-resistant HSV infection and their mechanism of action.

Using 2D and 3D pluripotent stem cell models to study neurotropic viruses

Understanding the impact of viral pathogens on the human central nervous system (CNS) has been challenging due to the lack of viable human CNS models for controlled experiments to determine the causal factors underlying pathogenesis. Human embryonic stem cells (ESCs) and, more recently, cellular reprogramming of adult somatic cells to generate human induced pluripotent stem cells (iPSCs) provide opportunities for directed differentiation to neural cells that can be used to evaluate the impact of known and emerging viruses on neural cell types. Pluripotent stem cells (PSCs) can be induced to neural lineages in either two- (2D) or three-dimensional (3D) cultures, each bearing distinct advantages and limitations for modeling viral pathogenesis and evaluating effective therapeutics. Here we review the current state of technology in stem cell-based modeling of the CNS and how these models can be used to determine viral tropism and identify cellular phenotypes to investigate virus-host interactions and facilitate drug screening. We focus on several viruses (e.g., human immunodeficiency virus (HIV), herpes simplex virus (HSV), Zika virus (ZIKV), human cytomegalovirus (HCMV), SARS-CoV-2, West Nile virus (WNV)) to illustrate key advantages, as well as challenges, of PSC-based models. We also discuss how human PSC-based models can be used to evaluate the safety and efficacy of therapeutic drugs by generating data that are complementary to existing preclinical models. Ultimately, these efforts could facilitate the movement towards personalized medicine and provide patients and physicians with an additional source of information to consider when evaluating available treatment strategies.

Synthesis of non-nucleoside anti-viral cyclopropylcarboxacyl hydrazones and initial anti-HSV-1 structure-activity relationship studies

The synthesis of a lead anti-viral cyclopropyl carboxy acyl hydrazone 4F17 (5) and three sequential arrays of structural analogues along with the initial assessment and optimization of the antiviral pharmacophore against the herpes simplex virus type 1 (HSV-1) are reported.

H-bond donor-directed switching of diastereoselectivity in the Michael addition of α-azido ketones to nitroolefins

The development of catalyst-controlled stereodivergent asymmetric catalysis is important for providing facile access to all stereoisomers of chiral products with multiple stereocenters from the same starting materials. Despite progress, new design strategies for diastereodivergent asymmetric catalysis are still highly desirable. Here we report the potency of H-bond donors as the governing factor to tune diastereoselectivity in a highly diastereoselective switchable enantioselective Michael addition of α-azido ketones to nitroolefins. While a newly developed bifunctional tertiary amine, phosphoramide, preferentially afforded syn-adducts, an analogous squaramide catalyst selectively gave anti-adducts. The resulting multifunctional tertiary azides can be converted to spiro-pyrrolidines with four continuous stereocenters in a one-pot operation. Mechanistic studies cast light on the control of diastereoselectivity by H-bond donors. While the squaramide-catalyzed reaction proceeded with a transition state with both squaramide N–H bonds binding to an enolate intermediate, an unprecedented model was proposed for the phosphoramide-mediated reaction wherein an amide N–H bond and an alkylammonium ion formed in situ interact with nitroolefins, with the enolate stabilized by nonclassical C–H⋯O hydrogen-bonding interactions.

We report the successful reversal of the diastereoselectivity in an unprecedented Michael addition of α-azido ketones to nitroolefins catalyzed by bifunctional tertiary amines, simply by varying the H-bond donor from phosphoramide to squaramide.

Modeling Herpes Simplex Virus 1 Infections in Human Central Nervous System Neuronal Cells Using Two- and Three-Dimensional Cultures Derived from Induced Pluripotent Stem Cells

Herpes simplex virus 1 (HSV-1) establishes latency in both peripheral nerve ganglia and the central nervous system (CNS). The outcomes of acute and latent infections in these different anatomic sites appear to be distinct. It is becoming clear that many of the existing culture models using animal primary neurons to investigate HSV-1 infection of the CNS are limited and not ideal, and most do not recapitulate features of CNS neurons. Human induced pluripotent stem cells (hiPSCs) and neurons derived from them are documented as tools to study aspects of neuropathogenesis, but few have focused on modeling infections of the CNS. Here, we characterize functional two-dimensional (2D) CNS-like neuron cultures and three-dimensional (3D) brain organoids made from hiPSCs to model HSV-1-human-CNS interactions. Our results show that (i) hiPSC-derived CNS neurons are permissive for HSV-1 infection; (ii) a quiescent state exhibiting key landmarks of HSV-1 latency described in animal models can be established in hiPSC-derived CNS neurons; (iii) the complex laminar structure of the organoids can be efficiently infected with HSV, with virus being transported from the periphery to the central layers of the organoid; and (iv) the organoids support reactivation of HSV-1, albeit less efficiently than 2D cultures. Collectively, our results indicate that hiPSC-derived neuronal platforms, especially 3D organoids, offer an extraordinary opportunity for modeling the interaction of HSV-1 with the complex cellular and architectural structure of the human CNS.IMPORTANCE This study employed human induced pluripotent stem cells (hiPSCs) to model acute and latent HSV-1 infections in two-dimensional (2D) and three-dimensional (3D) CNS neuronal cultures. We successfully established acute HSV-1 infections and infections showing features of latency. HSV-1 infection of the 3D organoids was able to spread from the outer surface of the organoid and was transported to the interior lamina, providing a model to study HSV-1 trafficking through complex neuronal tissue structures. HSV-1 could be reactivated in both culture systems; though, in contrast to 2D cultures, it appeared to be more difficult to reactivate HSV-1 in 3D cultures, potentially paralleling the low efficiency of HSV-1 reactivation in the CNS of animal models. The reactivation events were accompanied by dramatic neuronal morphological changes and cell-cell fusion. Together, our results provide substantive evidence of the suitability of hiPSC-based neuronal platforms to model HSV-1-CNS interactions in a human context.

The synthesis of densely functionalised α-acyloxy enaminals and enaminones via a novel homogeneous silver(i) catalysed rearrangement

A synthesis of densely functionalised α-acyloxy enaminals and enaminones via a novel homogeneous silver(i) catalyzed rearrangement of 1-acyloxy-3-azido ketones is reported.

Amaryllidaceae andSceletiumalkaloids

Recent progress on the isolation, identification, biological activity and synthetic studies of Amaryllidaceae alkaloids, as well as the structurally close alkaloids from theSceletiumgenus, published from July 2015 to June 2017 are reviewed.

R430: A potent inhibitor of DNA and RNA viruses

Acyclovir (ACV) is an effective antiviral agent for treating lytic Herpes Simplex virus, type 1 (HSV-1) infections, and it has dramatically reduced the mortality rate of herpes simplex encephalitis. However, HSV-1 resistance to ACV and its derivatives is being increasingly documented, particularly among immunocompromised individuals. The burgeoning drug resistance compels the search for a new generation of more efficacious anti-herpetic drugs. We have previously shown that trans-dihydrolycoricidine (R430), a lycorane-type alkaloid derivative, effectively inhibits HSV-1 infections in cultured cells. We now report that R430 also inhibits ACV-resistant HSV-1 strains, accompanied by global inhibition of viral gene transcription and enrichment of H3K27me3 methylation on viral gene promoters. Furthermore, we demonstrate that R430 prevents HSV-1 reactivation from latency in an ex vivo rodent model. Finally, among a panel of DNA viruses and RNA viruses, R430 inhibited Zika virus with high therapeutic index. Its therapeutic index is comparable to standard antiviral drugs, though it has greater toxicity in non-neuronal cells than in neuronal cells. Synthesis of additional derivatives could enable more efficacious antivirals and the identification of active pharmacophores.

Stereoselective synthesis of trans-dihydronarciclasine derivatives containing a 1,4-benzodioxane moiety

ABSTRACT

Some new trans-dihydronarciclasine derivatives containing a 1,4-benzodioxane moiety were stereoselectively synthesised using our feasible and efficient method developed recently. These new phenanthridone alkaloid analogues were obtained in both racemic and optically active forms. High enantioselectivities (up to 99% ee) were achieved by applying (8S,9S)-9-amino(9-deoxy)epiquinine as an organocatalyst. Due to a side reaction, various methoxyphenanthridine regioisomers were also prepared which afforded further synthetic trans-dihydronarciclasine analogues modified in the ring A of the phenanthridone scaffold.

GRAPHICAL ABSTRACT

Asymmetric Entry into 10b-aza-Analogues of Amaryllidaceae Alkaloids Reveals a Pronounced Electronic Effect on Antiviral Activity

Development of a chiral pool-based synthesis of 10b-aza-analogues of biologically active Amaryllidaceae alkaloids is described, involving a concise reductive amination and condensation sequence, leading to ring-B/C-modified, fully functionalized ring-C derivatives. Differentiated anticancer and antiviral activities of these analogues are presented. Despite complete conformational and functional group overlap, the 10b-aza-analogues have diminished anticancer activity and no antiviral activity. These unprecedented electronic effects suggest a possible role for π-type secondary orbital interactions with the biological target.

Asymmetric cinnamylation of N-tert-butanesulfinyl imines with cinnamyl acetates: total syntheses of (+)-lycoricidine and (+)-7-deoxypancratistatin

Highly diastereoselective palladium catalyzed cinnamylation of N-tert-butanesulfinyl imines with cinnamyl acetates has been established to provide enantioenriched β-aryl homoallylic amines. The synthetic application of this stragety has been successfully demonstrated in the concise total syntheses of antitumor natural products (+)-lycoricidine and (+)-7-deoxypancratistatin.

Catalytic enantioselective synthesis of α-chiral azides

The catalytic asymmetric synthesis of α-chiral azides is of current interest and three synthetic strategies have been developed. This review summarizes the recent progress in this research area, discusses the advantages and limitations of each strategy, and outlines synthetic opportunities for future research.

Comparison of three cell-based drug screening platforms for HSV-1 infection

Acyclovir (ACV) and its derivatives have been highly effective for treating recurrent, lytic infections with Herpes Simplex Virus, type 1 (HSV-1), but searches for additional antiviral drugs are motivated by recent reports of resistance to ACV, particularly among immunocompromised patients. In addition, the relative neurotoxicity of ACV and its inability to prevent neurological sequelae among HSV-1 encephalitis survivors compel searches for new drugs to treat HSV-1 infections of the central nervous system (CNS). Primary drug screens for neurotropic viruses like HSV-1 typically utilize non-neuronal cell lines, but they may miss drugs that have neuron specific antiviral effects. Therefore, we compared the effects of a panel of conventional and novel anti-herpetic compounds in monkey epithelial (Vero) cells, human induced pluripotent stem cells (hiPSCs)-derived neural progenitor cells (NPCs) and hiPSC-derived neurons (N = 73 drugs). While the profiles of activity for the majority of the drugs were similar in all three tissues, Vero cells were less likely than NPCs to identify drugs with substantial inhibitory activity in hiPSC-derived neurons. We discuss the relative merits of each cell type for antiviral drug screens against neuronal infections with HSV-1.