Acridine and phenothiazine derivatives as pharmacotherapeutics for prion disease

Abstract

Prion diseases in humans and animals are invariably fatal. Prions are composed of a disease-causing isoform (PrP Sc ) of the normal host prion protein (PrP C ) and replicate by stimulating the conversion of PrP C into nascent PrP Sc . We report here that tricyclic derivatives of acridine and phenothiazine exhibit half-maximal inhibition of PrP Sc formation at effective concentrations (EC50) between 0.3 M and 3 M in cultured cells chronically infected with prions. The EC 50 for chlorpromazine was 3 M, whereas quinacrine was 10 times more potent. A variety of 9-substituted, acridine-based analogues of quinacrine were synthesized, which demonstrated variable antiprion potencies similar to those of chlorpromazine and emphasized the importance of the side chain in mediating the inhibition of PrP Sc formation. Thus, our studies show that tricyclic compounds with an aliphatic side chain at the middle ring moiety constitute a new class of antiprion reagents. Because quinacrine and chlorpromazine have been used in humans for many years as antimalarial and antipsychotic drugs, respectively, and are known to pass the blood-brain barrier, we suggest that they are immediate candidates for the treatment of Creutzfeldt-Jakob disease and other prion diseases. P rion diseases are uniquely manifest as spontaneous, inherited, and infectious maladies. These diseases include Gerstmann-Sträussler-Scheinker (GSS) disease, fatal insomnia, and Creutzfeldt-Jakob disease (CJD). Most cases of CJD are sporadic with 10-15% being inherited (1). Although the infectious human prion diseases are most notorious, they account for less than 1% of all prion disorders (2). Concern about these infectious disorders has been heightened by the identification of more than 100 young adults and teenagers who have developed new variant CJD (nvCJD) in Europe after exposure to bovine prions from cattle with bovine spongiform encephalopathy (BSE; refs. 3 and 4). Other infectious prion diseases include kuru, which is found among New Guinea natives and is caused by ritualistic cannibalism, and iatrogenic CJD, which is caused by prioncontaminated cadaveric growth hormone and dura mater grafts (2,5,6).A wealth of experimental data indicates that prions are composed solely of a misfolded prion protein (PrP) isoform (PrP Sc ) of a glycolipid-anchored host protein (PrP C ; refs. 7 and 8). Unlike all other infectious agents, prions are devoid of nucleic acid (9, 10). For years, the existence of prion strains caused many investigators to argue that a small nucleic acid encodes prion diversity (11). Eventually, convincing data accumulated arguing that prion diversity is enciphered in the conformation of PrP Sc (3,12,13).Patients with CJD and other prion diseases develop progressive neurologic dysfunction. Prion diseases are invariably fatal, and death frequently occurs in less than 1 year after the first symptoms appear (2). No effective therapy exists for prion diseases in humans or animals (14).Many compounds have been identified that inhibit prion propagation when adm...

Canine MDCK cell lines are refractory to infection with human and mouse prions

“…One of the most commonly used cell line for in vitro prion studies is the mouse neuroblastoma cell line N2a which is readily susceptible to mouse adapted sheep scrapie prion strains. In fact, these cells can become chronically infected with the prion agent and have served as an in vitro model for testing potential therapeutic approaches against prion diseases [21,39]. Several recent reports demonstrated that non-neuronal cells can also support TSE infection.…”

Parallel synthesis of 9-aminoacridines and their evaluation against chloroquine-resistant Plasmodium falciparum

“…The solution was cooled to °C, treated with Et 2 O (500 ml), and extracted with HCl (1M aq., 2×300 ml). The combined aqueous layers were washed with Et 2 O (200 ml), cooled to 0 °C , treated directly with solid NaOH until the mixture was visibly heterogeneous, and then extracted with EtOAc (3×200 ml), dried over Na 2 SO 4 , and concentrated in vacuo to yield the desired secondary amines (15) in high purity (50-71% yield).…”

CD and NMR Studies of Prion Protein (PrP) Helix 1

“…Thus, a cluster of aromatic residues is formed in the peptide, which is solvent-exposed to a large part even in the structure of PrP. In addition to its importance for the stability of helix 1 itself and for the attachment of helix 1 to helices 2 and 3, this cluster of aromatic residues may play an important role for the binding of potential therapeutic drugs such as quinacrine (49). 2 Our data underline the importance of interleaved placement of i,iϩ4 electrostatic and aromatic interactions for the formation of stable helices.…”