Curcumin as a natural potential drug candidate against important zoonotic viruses and prions: A narrative review.

Zoonotic diseases are major public health concerns and undeniable threats to human health. Among Zoonotic diseases, zoonotic viruses and prions are much more difficult to eradicate, as they result in higher infections and mortality rates. Several investigations have shown curcumin, the active ingredient of turmeric, to have wide spectrum properties such as anti-microbial, anti-vascular, anti-inflammatory, anti-tumor, anti-neoplastic, anti-oxidant, and immune system modulator properties. In the present study, we performed a comprehensive review of existing in silico, in vitro, and in vivo evidence on the antiviral (54 important zoonotic viruses) and anti-prion properties of curcumin and curcuminoids in PubMed, Google Scholar, Science Direct, Scopus, and Web of Science databases. Database searches yielded 13,380 results, out of which 216 studies were eligible according to inclusion criteria. Of 216 studies, 135 (62.5%), 24 (11.1%), and 19 (8.8%) were conducted on the effect of curcumin and curcuminoids against SARS-CoV-2, Influenza A virus, and dengue virus, respectively. This review suggests curcumin and curcuminoids as promising therapeutic agents against a wide range of viral zoonoses by targeting different proteins and signaling pathways.

Sephin1 Reduces Prion Infection in Prion-Infected Cells and Animal Model.

Prion diseases are fatal infectious neurodegenerative disorders in human and animals caused by misfolding of the cellular prion protein (PrPC) into the infectious isoform PrPSc. These diseases have the potential to transmit within or between species, and no cure is available to date. Targeting the unfolded protein response (UPR) as an anti-prion therapeutic approach has been widely reported for prion diseases. Here, we describe the anti-prion effect of the chemical compound Sephin1 which has been shown to protect in mouse models of protein misfolding diseases including amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS) by selectively inhibiting the stress-induced regulatory subunit of protein phosphatase 1, thus prolonging eIF2α phosphorylation. We show here that Sephin1 dose and time dependently reduced PrPSc in different neuronal cell lines which were persistently infected with various prion strains. In addition, prion seeding activity was reduced in Sephin1-treated cells. Importantly, we found that Sephin1 significantly overcame the endoplasmic reticulum (ER) stress induced in treated cells, as measured by lower expression of stress-induced aberrant prion protein. In a mouse model of prion infection, intraperitoneal treatment with Sephin1 significantly prolonged survival of prion-infected mice. When combining Sephin1 with the neuroprotective drug metformin, the survival of prion-infected mice was also prolonged. These results suggest that Sephin1 could be a potential anti-prion drug selectively targeting one component of the UPR pathway.

Anti-prion drug screening system in Saccharomyces cerevisiae based on an artificial [LEU2+] prion.

Proteinaceous infectious particles causing mammalian transmissible spongiform encephalopathies or prions are being extensively studied. However due to their hazardous nature, the initial screening of potential anti-prion drugs is often made in a yeast-based screening system utilizing a well-characterized [PSI+] prion (amyloid formed by the translation termination factor Sup35p). In the [PSI+] prion screening system (white/red colony assay), the prion phenotype yields white colonies while addition of an anti-prion drug will yield red colonies. However, this system has some limitations. It is difficult to quantify the effectiveness of the anti-prion compound, the diffusion of the studied compound may affect the result, and the deficiency of glutathione in cells may prevent the formation of red pigment in cured cells. Therefore, alternative yeast prion screening systems are still needed. This article aims to present an alternative yeast-based system to evaluate anti-prion activity of chemical compounds. The method that was used is based on an artificial [LEU2+] prion created by fusing Leu2p with the prion-forming domain of Sup35p in Saccharomyces cerevisiae. Phenotypic analysis and semi-denaturating detergent agarose gel electrophoresis (SDD-AGE) confirmed the presence of the artificial [LEU2+] prion in yeast cells. This screening system verified the anti-prion activity of 3 drugs that were found to have been active in the white/red colony assay, while one compound (6-chlorotacrine) that was active in the white/red colony assay was found to be inactive in the [LEU2+] system. This new system also appears to be more sensitive than the white/red colony assay.

Synthesis of monomeric and dimeric acridine compounds as potential therapeutics in Alzheimer and prion diseases.

Starting from substituted 9-chloroacridines, a series of quinacrine and spacered dimeric acridine compounds was prepared. Their ability to interrupt the protein association of prion- and Alzheimer-specific proteins and Ab peptides was explored using a fast screening system based on FACS analysis. The bis-acridines displayed a higher activity than the corresponding monomers. Among these derivatives, best results were obtained with the 2,4-dimethoxy-6-nitro compound 7h for Abeta-peptides and the 2-methoxy-6-nitro compound 7f for PrP.

Procedure for identification and characterization of drugs efficient against mammalian prion: from a yeast-based antiprion drug screening assay to in vivo mouse models.

Prion diseases are fatal and incurable infectious neurodegenerative disorders affecting humans and other mammals. Prions are composed essentially if not solely of PrP(Sc), a misfolded form of the host-encoded PrP protein. PrP(Sc) catalyzes the transconformation of the normal endogenous PrP (PrP(C)) into more PrP(Sc). Prion replication thus corresponds to the propagation of an altered folding state of PrP. Several prion proteins have also been identified in the simple model organism Saccharomyces cerevisiae. Yeast prion-based screening assays have allowed identification of drugs active against mammalian prions, thus revealing the existence of common prion propagation mechanisms conserved from yeast to human. To identify these conserved targets, antiprion compounds isolated in yeast can be used as baits in reverse screening strategies. Once identified, these targets could in turn lead to the development of mechanism-based cell-free antiprion screening assays. A reverse screening procedure has been performed for 6AP and GA, two antiprion compounds isolated using a yeast-based assay. Protein folding activity of the large ribosomal RNA was found to be a physical and a functional target of both 6AP and GA therefore suggesting that this activity of the ribosome may constitute a novel mechanism involved in prion propagation and, as a consequence, a new screening target.

Influence of phosphorus dendrimers on the aggregation of the prion peptide PrP 185-208.

Inhibition of fibril assembly is a potential therapeutic strategy in prion diseases. The effect of cationic phosphorous dendrimers on the aggregation process of the prion peptide PrP 185-208 was studied using a spectrofluorometric assay with thioflavin T (ThT) and Fourier transformed infrared spectroscopy in order to monitor the kinetics of the process and the changes in the peptide secondary structure. The results show that phosphorous dendrimers are able to clearly interfere with PrP 185-208 aggregation process by both slowing down the formation of aggregates (by causing a decrease of the nucleation rate) and by lowering the final amount of amyloid fibrils, a common hallmark of conformational diseases. The dendrimers effect on the aggregation process would imply their interaction with peptide monomers and oligomers during the nucleation phase.

Exposure to low dietary copper or low copper coupled with high dietary manganese for one year does not alter brain prion protein characteristics in the mature cow.

It is now widely accepted that abnormal prion proteins are the likely causative agent in bovine spongiform encephalopathy. Cellular prion proteins (PrP(c)) bind Cu, which appears to be required to maintain functional characteristics of the protein. The replacement of Cu on PrP(c) with Mn has resulted in loss of function and increased protease resistance. Twelve mature cows were used to determine the effects of Cu deficiency, alone and coupled with high dietary Mn, on brain Cu and Mn concentrations and on PrP(c) functional characteristics. Copper-adequate cows were randomly assigned to treatments: 1) control (adequate in Cu and Mn), 2) Cu-deficient (-Cu), and 3) Cu-deficient plus high dietary Mn (-Cu+Mn). Cows assigned to treatments -Cu and -Cu+Mn received no supplemental Cu and were supplemented with Mo to further induce Cu deficiency. After 360 d, Cu-deficient cows (-Cu and -Cu+Mn) tended to have lesser concentrations of Cu (P = 0.09) in the obex region of the brain stem. Brain Mn tended (P = 0.09) to be greater in -Cu+Mn cattle compared with -Cu cattle. Western blots revealed that PrP(c) relative optical densities, proteinase K degradability, elution profiles, molecular weights, and glycoform distributions were not different among treatments. The concentration of PrP(c), as determined by ELISA, was similar across treatment groups. Brain tissue (obex) Mn superoxide dismutase activity was greatest (P = 0.04) in cattle receiving -Cu+Mn, whereas immunopurified PrP(c) had similar superoxide dismutase-like activities among treatments. Immunopurified PrP(c) had similar Cu concentrations across treatments, whereas Mn was undetectable. We concluded that Cu deficiency, coupled with excessive Mn intake, in the bovine may decrease brain Cu and increase brain Mn. Copper deficiency, alone or coupled with high dietary Mn, did not cause detectable alterations in PrP(c) functional characteristics.

Prevention of prion propagation by dehydrocholesterol reductase inhibitors in cultured cells and a therapeutic trial in mice.

In prion diseases, the normal cellular form of prion protein (PrP(C)) is converted into the disease-associated isoforms (PrP(Sc)) which accumulate in the infected tissues. Although the precise mechanism of this conversion remains unsolved, drugs of various categories have been reported to reduce the accumulation of PrP(Sc) in prion-infected cultured cells. We here show that AY-9944 (a 7-dehydrocholesterol reductase inhibitor) and U18666A (a 24-dehydrocholesterol reductase inhibitor) prevent PrP(Sc) from accumulating in prion-infected mouse neuroblastoma cells (ScN2a), with an ED50 of about 0.5 microM and 10 nM, respectively. In order to evaluate the efficacy of these two inhibitors in vivo, C57BL/6J mice inoculated with mouse-adapted scrapie-prion received repetitive intraperitoneal injections of U18666A (10 mg/kg) or a mixture of U18666A (10 mg/kg) and AY-9944 (12 mg/kg). By contrast to the potent anti-prion effects observed in ScN2a cells, the in vivo trial was abortive with neither drug halting the progression of the disease.

Chelating compound, chrysoidine, is more effective in both antiprion activity and brain endothelial permeability than quinacrine.

1. As an extension of our previous study of quinacrine and its derivatives, chelating chemicals were screened to obtain more effective, better brain-permeable antiprion compounds using either prion-infected neuroblastoma cells or brain capillary endothelial cells.2. Eleven chemicals were found to have antiprion activity. Most of them shared a common structure consisting of benzene or naphthalene at either end of an azo bond. Structure-activity data suggest that chelating activity is not necessary but might contribute to the antiprion action.3. Chrysoidine, a representative compound found here, was about 27 times more effective in the antiprion activity and five times more efficiently permeable through the brain capillary endothelial cells than quinacrine was.4. These chemicals might be useful as compounds for development of therapeutics for prion diseases.

Surface plasmon resonance analysis for the screening of anti-prion compounds.

The interaction of anti-prion compounds and amyloid binding dyes with a carboxy-terminal domain of prion protein (PrP121-231) was examined using surface plasmon resonance (SPR) and compared with inhibition activities of abnormal PrP formation in scrapie-infected cells. Most examined compounds had affinities for PrP121-231: antimalarials had low affinities, whereas Congo red, phthalocyanine and thioflavin S had high affinities. The SPR binding response correlated with the inhibition activity of abnormal PrP formation. Several drugs were screened using SPR to verify the findings: propranolol was identified as a new anti-prion compound. This fact indicates that drug screenings by this assay are useful.

Translation elongation-3-like factors: are they rational antifungal targets?

The occurrence of fungal infection has escalated significantly in recent years and is expected to continue to increase for the foreseeable future. Unfortunately, only a limited number of antifungal drugs are currently available partially due to a lack of suitable targets. The most commonly used antifungals target the same molecule in the cell membrane and, while efficacious, are either extremely toxic or susceptible to resistance. This article examines elongation factor-3, which is unique to fungi and essential for fungal cell survival and, thus, an attractive antifungal target. A search for inhibitors of this 'perfect target' led to identification of compounds (sordarins) which inhibited elongation factor-2, a protein with a mammalian homologue. Molecular analysis demonstrated why sordarins can specifically act against fungal elongation factor-2. This data questions the validity of pursuing genes as targets only if they are unique to fungi. Proteins that are homologous to elongation factor-3 are also discussed. The advances in molecular techniques and bioinformatics will allow the re-evaluation of targets previously thought to be unattractive. In addition, molecular genetics provides new and novel information on cellular processes that can potentially introduce new targets.

Mimicking dominant negative inhibition of prion replication through structure-based drug design.

Recent progress determining the structure of the host-encoded prion protein (PrP(C)) and the role of auxiliary molecules in prion replication permits a more rational approach in the development of therapeutic interventions. Our objective is to identify a new class of lead compounds that mimic the dominant negative PrP(C) mutants, which inhibit an abnormal isoform (PrP(Sc)) formation. A computational search was conducted on the Available Chemicals Directory for molecules that mimic both the spatial orientation and basic polymorphism of PrP residues 168, 172, 215, and 219, which confer dominant negative inhibition. The search revealed 1,000 potential candidates that were visually analyzed with respect to the structure of this four-residue epitope on PrP(C). Sixty-three compounds were tested for inhibition of PrP(Sc) formation in scrapie-infected mouse neuroblastoma cells (ScN2a). Two compounds, Cp-60 (2-amino-6-[(2-aminophenyl)thio]-4-(2-furyl)pyridine-3, 5-dicarbonitrile) and Cp-62 (N'1-(¿5-[(4, 5-dichloro-1H-imidazol-1-yl)methyl]-2-furyl¿carbonyl)-4 methoxybenzene-1-sulfonohydrazide), inhibited PrP(Sc) formation in a dose-dependent manner and demonstrated low levels of toxicity. A substructure search of the Available Chemicals Directory based on Cp-60 identified five related molecules, three of which exhibited activities comparable to Cp-60. Mimicking dominant negative inhibition in the design of drugs that inhibit prion replication may provide a more general approach to developing therapeutics for deleterious protein-protein interactions.

High-dose exposure to systemic phosmet insecticide modifies the phosphatidylinositol anchor on the prion protein: the origins of new variant transmissible spongiform encephalopathies?

Compulsory exposure of the UK bovine to exclusively high biannual doses of a 'systemic' pour-on formulation of an organo-phthalimido-phosphorus warblecide, phosmet, during the 1980s (combined with exposure to the lipid-bound residues of 'bioconcentrated' phosmet recycled back via the intensive feeding of meat and bone meal), initiated the 'new strain' modification of the CNS prion protein (PrP) causing the UK's bovine spongiform encephalopathy (BSE) epidemic. A lipophilic solution of phosmet was poured along the bovine's spinal column, whence it penetrated and concentrated in phospholipids of the CNS membranes, covalently modifying endogenous phosphorylation sites on phosphatidylinositols (PIs) etc., forming a 'toxic membrane bank' of abnormally modified lipids that 'infect' any membrane proteins (such as PrP) that are programmed to conjugate onto them for anchorage to the membrane. Thus, phosmet invokes a primary covalent modification on PrP's PI anchor which, in turn, invokes an overall diverse disturbance upon CNS phosphoinositide second messenger feed back cycle, calcium homeostasis and essential free radicals; thus initiating a self-perpetuating cascade of abnormally phosphorylated PI-PrP that invokes a secondary electrostatic and allosteric disturbance on the main body of PrP impairing tertiary folding. Chaperone stress proteins conjugate onto misfolded PrP blocking its sites of proteolytic cleavage. Fresh epidemiological evidence is presented and experimental evidence referenced that adds support to a multifactorial hypothesis which proposes that BSE is a hitherto unrecognized and previously unmanifested class of subtle chronic phosmet-induced delayed neuro-excitotoxicity in the susceptible bovine.

Sulfated polyanion inhibition of scrapie-associated PrP accumulation in cultured cells.

The accumulation of an abnormal, protease-resistant form of the protein PrP (PrP-res) in hosts with scrapie and related transmissible spongiform encephalopathies appears to be important in disease pathogenesis. To gain insight into the mechanism of PrP-res accumulation and the in vivo antiscrapie activity of certain polyanions, we have studied effects of sulfated glycans on PrP metabolism in scrapie-infected neuroblastoma cells. Pentosan polysulfate, like the amyloid-binding dye Congo red, potently inhibited the accumulation of PrP-res in these cells without apparent effects on the metabolism of the normal isoform. The inhibition was due primarily to prevention of new PrP-res accumulation rather than destabilization of preexisting PrP-res. PrP-res accumulation remained depressed in the cultures after removal of the inhibitors. The activities of other sulfated glycans, nonsulfated polyanions, dextran, and DEAE-dextran were compared with those of pentosan polysulfate and Congo red. This comparison provided evidence that the density of sulfation and molecular size are factors influencing anti-PrP-res activity of sulfated glycans. The relative potencies of these compounds corresponded well with their previously determined antiscrapie activities in vivo, suggesting that the prophylactic effects of sulfated polyanions may be due to inhibition of PrP-res accumulation. Since PrP-res amyloid is known to contain sulfated glycosaminoglycans, we reason that these inhibitors may competitively block an interaction between PrP and endogenous glycosaminoglycans that is essential for its accumulation in a protease-resistant, potentially amyloidogenic state.

The possible role of substances inhibiting protein synthesis on the treatment of the spongiform encephalopathies.

The transmissible spongiform encephalopathies are probably caused by infectious proteinaceous agents called prions. It is suggested that these encephalopathies may be amenable to treatment by substances which inhibit protein synthesis.