Activities of<scp>dl</scp>-α-Difluoromethylarginine and Polyamine Analogues against<i>Cryptosporidium parvum</i>Infection in a T-Cell Receptor Alpha-Deficient Mouse Model

Yarlett, Nigel; Waters, W. Ray; Harp, James A.; Wannemuehler, Michael J.; Morada, Mary; Bellcastro, Josephine; Upton, Steve J.; Marton, Laurence J.; Frydman, Benjamiǹ

doi:10.1128/aac.01040-06

Cited by 12 publications

(6 citation statements)

References 34 publications

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“…The EC 50 value for L-arginine increased several fold in the presence of ADC inhibitor. DFMA is a specific inhibitor of ADC [37] and its specificity in our system was verified by the absence of any effect on agmatine-mediated vessel relaxation (Fig. 1b).…”

Section: Resultsmentioning

confidence: 63%

Agmatine induced NO dependent rat mesenteric artery relaxation and its impairment in salt-sensitive hypertension

et al. 2013

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L-arginine and its decarboxylated product, agmatine are important mediators of NO production and vascular relaxation. However, the underlying mechanisms of their action are not understood. We have investigated the role of arginine and agmatine in resistance vessel relaxation of Sprague-Dawley (SD) and Dahl salt-sensitive hypertensive rats. Second or 3rd-order mesenteric arterioles were cannulated in an organ chamber, pressurized and equilibrated before perfusing intraluminally with agonists. The vessel diameters were measured after mounting on the stage of a microscope fitted with a video camera. The gene expression in Dahl rat vessel homogenates was ascertained by real-time PCR. L-arginine initiated relaxations (EC50, 5.8 ± 0.7 mM; n = 9) were inhibited by arginine decarboxylase (ADC) inhibitor, difluoromethylarginine (DFMA) (EC50, 18.3 ± 1.3 mM; n = 5) suggesting that arginine-induced vessel relaxation was mediated by agmatine formation. Agmatine relaxed the SD rat vessels at significantly lower concentrations (EC50, 138.7 ± 12.1 μM; n = 22), which was compromised by L-NAME (L-NG-Nitroarginine methyl ester, an eNOS inhibitor), RX821002 (α-2 AR antagonist) and pertussis toxin (G-protein inhibitor). The agmatine-mediated vessel relaxation from high salt Dahl rats was abolished as compared to that from normal salt rats (EC50, 143.9 ± 23.4 μM; n = 5). The α-2A AR, α-2B AR and eNOS mRNA expression was downregulated in mesenteric arterioles of high-salt treated Dahl hypertensive rats. These findings demonstrate that agmatine facilitated the relaxation via activation of α-2 adrenergic G-protein coupled receptor and NO synthesis, and this pathway is compromised in salt-sensitive hypertension.

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Section: Resultsmentioning

confidence: 63%

Agmatine induced NO dependent rat mesenteric artery relaxation and its impairment in salt-sensitive hypertension

et al. 2013

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“…BKI-1294 has demonstrated efficacy in a mouse model of chronic cryptosporidiosis when dosed once per day for ten consecutive days at 100 mg/kg [ 23 ]. Active compounds have also emerged from screens for inhibitors of inosine-5’-monophosphate dehydrogenase [ 26 ], and polyamine analogues [ 27 ]. Despite these efforts there remains a dearth of compounds in the drug discovery pipeline, a limited biological understanding, and a lack of available tools to study this parasite.…”

Section: Introductionmentioning

confidence: 99%

A high-throughput phenotypic screen identifies clofazimine as a potential treatment for cryptosporidiosis

et al. 2017

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Cryptosporidiosis has emerged as a leading cause of non-viral diarrhea in children under five years of age in the developing world, yet the current standard of care to treat Cryptosporidium infections, nitazoxanide, demonstrates limited and immune-dependent efficacy. Given the lack of treatments with universal efficacy, drug discovery efforts against cryptosporidiosis are necessary to find therapeutics more efficacious than the standard of care. To date, cryptosporidiosis drug discovery efforts have been limited to a few targeted mechanisms in the parasite and whole cell phenotypic screens against small, focused collections of compounds. Using a previous screen as a basis, we initiated the largest known drug discovery effort to identify novel anticryptosporidial agents. A high-content imaging assay for inhibitors of Cryptosporidium parvum proliferation within a human intestinal epithelial cell line was miniaturized and automated to enable high-throughput phenotypic screening against a large, diverse library of small molecules. A screen of 78,942 compounds identified 12 anticryptosporidial hits with sub-micromolar activity, including clofazimine, an FDA-approved drug for the treatment of leprosy, which demonstrated potent and selective in vitro activity (EC50 = 15 nM) against C. parvum. Clofazimine also displayed activity against C. hominis–the other most clinically-relevant species of Cryptosporidium. Importantly, clofazimine is known to accumulate within epithelial cells of the small intestine, the primary site of Cryptosporidium infection. In a mouse model of acute cryptosporidiosis, a once daily dosage regimen for three consecutive days or a single high dose resulted in reduction of oocyst shedding below the limit detectable by flow cytometry. Recently, a target product profile (TPP) for an anticryptosporidial compound was proposed by Huston et al. and highlights the need for a short dosing regimen (< 7 days) and formulations for children < 2 years. Clofazimine has a long history of use and has demonstrated a good safety profile for a disease that requires chronic dosing for a period of time ranging 3–36 months. These results, taken with clofazimine’s status as an FDA-approved drug with over four decades of use for the treatment of leprosy, support the continued investigation of clofazimine both as a new chemical tool for understanding cryptosporidium biology and a potential new treatment of cryptosporidiosis.

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“…Due to the technical challenges to work with this notoriously intractable parasite, early drug discovery efforts for cryptosporidiosis treatment have been limited to a few targeted mechanisms, − e.g., fatty acyl-CoA binding protein (CpACBP1), calcium-dependent protein kinases (CDPKs), and inosine-5′-monophosphate dehydrogenase (IMPDH), in the parasite. The drug discovery process has been facilitated with the establishment of the whole cell phenotypic screening platforms for inhibitors of C. parvum proliferation within human intestinal epithelial HCT-8 cells, , leading to the discovery of lead compounds, e.g., clofazimine and KDU731, which showed submicromolar inhibitory activities.…”

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confidence: 99%

Herbicidins from Streptomyces sp. CB01388 Showing Anti-Cryptosporidium Activity

et al. 2018

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A high-content imaging assay was used to screen the fraction collection of the Natural Product Library at The Scripps Research Institute for inhibitors of Cryptosporidium parvum. A chemical investigation of one strain, Streptomyces sp. CB01388, resulted in the isolation of six herbicidins (1-6), one of which is new (herbicidin L, 1). Five of the six herbicidins (1-3, 5, 6) showed moderate inhibitory activity against C. parvum, with 1 and 6 comparable to the FDA-approved drug nitazoxanide, and 2-6 showed no toxicity to the host HCT-8 cells and human HEK293T and HepG2 cells. These findings highlight the herbicidin scaffold for anti- Cryptosporidium drug development.

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Activities ofdl-α-Difluoromethylarginine and Polyamine Analogues againstCryptosporidium parvumInfection in a T-Cell Receptor Alpha-Deficient Mouse Model

Cited by 12 publications

References 34 publications

Agmatine induced NO dependent rat mesenteric artery relaxation and its impairment in salt-sensitive hypertension

Agmatine induced NO dependent rat mesenteric artery relaxation and its impairment in salt-sensitive hypertension

A high-throughput phenotypic screen identifies clofazimine as a potential treatment for cryptosporidiosis

Herbicidins from Streptomyces sp. CB01388 Showing Anti-Cryptosporidium Activity

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