Biology subjects

Spangenberg, T.

Publications and source records attributed to Spangenberg, T..

3 recordsLinked to original sources

bioRxiv2024

Real-Time Imaging of Antimalarial Drug Effects on Plasmodium falciparum-Infected Red Blood Cells

Malaria remains a significant global health challenge, exacerbated by emerging drug resistance, which has been recurring ever since Chloroquine resistance was reported to spread in the 1960s. Cabamiquine (M5717), a promising antimalarial candidate, targets Plasmodium falciparum elongation factor 2 (PfeEF2) and has demonstrated high potency and multi-stage activity. However, differences in parasite-killing kinetics require further exploration. This proof-of-concept study employs time-lapse microscopy to assess the effects of Chloroquine and Cabamiquine on P. falciparum-infected red blood cells. Using a fluorogenic DNA dye, we monitored morphological changes and cell death at the single-cell level. Unlike the faster-killing Chloroquine, our findings confirm a lag phase of the effect of Cabamiquine and reveal a delay before host cell lysis. This delayed cytotoxic effect underscores the cytostatic phase of the drug prior to killing and highlights its potential in combination therapies. Our novel imaging approach provides a comprehensive fingerprinting method to quantify cytostatic, cytotoxic, and cytolytic activities of antimalarial drugs, offering valuable insights into their mechanisms of action at a cellular level therefore enabling to discriminate the steps prior to parasite clearance in hosts.

cell biology↗

bioRxiv2023

Identification of potent and orally efficacious phosphodiesterase inhibitors in Cryptosporidium parvum-infected immunocompromised mice

Cryptosporidium species, mostly C. parvum and C. hominis in humans, are intestinal apicomplexan parasites that cause life-threatening diarrhea in young children and people with cell-mediated immune defects, such as due to AIDS. There is only one approved treatment for cryptosporidiosis, but it is ineffective for immunocompromised people and only modestly effective for children. In this study, screening 278 compounds from the Merck KGaA, Darmstadt, Germany collection and accelerated follow-up work enabled by prior investigation of the compounds resulted in identification of a series of pyrazolopyrimidine human phosphodiesterase (PDE)-V inhibitors with potent anticryptosporidial activity and efficacy following oral administration in C. parvum-infected immunocompromised mice. The novel PDE inhibitor leads (compounds PDEi2 and PDEi5) affect parasite egress from infected host cells. They have comparable activity against C. parvum and C. hominis, rapidly eliminate C. parvum in tissue culture, and have minimal off-target effects in a panel of safety screening assays. In comparison, the potent human PDE-V inhibitors sildenafil and the 4-aminoquinoline compound 7a have no useful activity against C. parvum. Based on homology modeling and in silico compound docking, PDEi5 interacts directly with an active-site metal ion and docks well to two C. parvum PDEs. In contrast, larger amino acid side groups (Val900/Tyr11128 and His884/Asn1112) in both C. parvum PDEs replace alanine in human PDE-V and block sildenafil binding, explaining its lack of efficacy. These results identify a promising new drug target and lead series for anticryptosporidial drug development and validates a route to target-based optimization.

microbiology↗

bioRxiv2021

Mechanism of praziquantel action at a parasitic flatworm ion channel

Praziquantel (PZQ) is an essential medicine for treating parasitic flatworm infections such as schistosomiasis, which afflicts over 250 million people. However, PZQ is not universally effective, lacking activity against the liver fluke Fasciola. The reason for this insensitivity is unclear, as the mechanism of PZQ action is unknown. Here, we show PZQ activates a transient receptor potential melastatin ion channel (TRPMPZQ) in schistosomes by engaging a hydrophobic ligand binding pocket within the voltage-sensor like domain to cause Ca2+ entry and worm paralysis. PZQ activates TRPMPZQ homologues in other PZQ-sensitive flukes, but not Fasciola. However, a single amino acid change in the Fasciola TRPMPZQ binding pocket, to mimic schistosome TRPMPZQ, confers PZQ sensitivity. After decades of clinical use, the basis of PZQ action at a druggable TRP channel is resolved.

pharmacology and toxicology↗