Limited Inhibitory Effects of Oseltamivir and Zanamivir on Human Sialidases

Abstract

Oseltamivir (Tamiflu) and zanamivir (Relenza), two extensively used clinically effective anti-influenza drugs, are viral sialidase (also known as neuraminidase) inhibitors that prevent the release of progeny virions and thereby limit the spread of infection. Recently mortalities and neuropsychiatric events have been reported with the use of oseltamivir, especially in pediatric cases in Japan, suggesting that these drugs might also inhibit endogenous enzymes involved in sialic acid metabolism, including sialidase, sialyltransferase, and CMPsynthase, in addition to their inhibitory effects on the viral sialidase. The possible inhibition could account for some of the rare side effects of oseltamivir. However, there has been little direct evidence in regard to the sensitivities of animal sialidases to these drugs. Here, we examined whether these inhibitors might indeed affect the activities of human sialidases, which differ in primary structures and enzyme properties but possess tertiary structures similar to those of the viral enzymes. Using recombinant enzymes corresponding to the four human sialidases identified so far, we found that oseltamivir carboxylate scarcely affected the activities of any of the sialidases, even at 1 mM, while zanamivir significantly inhibited the human sialidases NEU3 and NEU2 in the micromolar range (K i , 3.7 ؎ 0.48 and 12.9 ؎ 0.07 M, respectively), providing a contrast to the low nanomolar concentrations at which these drugs block the activity of the viral sialidases.

An intrinsic mechanism of secreted protein aging and turnover

“…The contributions of Neu1 and Neu3 were investigated by pharmacological inhibition. The compound 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (DANA) is a broad-spectrum neuraminidase inhibitor of all four Neu isozymes, whereas zanamivir inhibits Neu2, Neu3, and Neu4 but does not significantly inhibit Neu1 (14,15). The i.v.…”

Regulation of Sialyl Lewis Antigen Expression in Colon Cancer Cells by Sialidase NEU4

“…Because we previously found that expression of NEU2 and NEU4L was hardly detectable in colon mucosa and cancer (22,24), NEU1, NEU3, or NEU4S genes were introduced. First, we observed NEU4S effects on the sialyl-Le a and sialyl-Le x expression, because of its broad substrate specificity (19).…”

“…The ORF of human NEU4S tagged with HA at the C-terminal was subcloned into pcDNA 3.1 (Invitrogen), and a pCAGGS expression plasmid (a generous gift from Dr. Miyazaki, Osaka University School of Medicine), and then transfected with Lipofectamine 2000 reagent (Invitrogen). Expression vectors for NEU1, NEU2, and NEU3 were prepared as previously reported (24), and for NEU1 expression, the plasmid for the protective protein (carboxypeptidase A) pp11 gene was co-transfected (16). To obtain stable transfectants, G418 (Sigma) was used with HT29 cells at 600 g/ml and with DLD-1 at 300 g/ml.…”

“…For sialidase activity assays, homogenates were prepared in PBS buffer containing leupeptin, pepstatin, PMSF, and 1 mM EDTA using transfected cells as the enzyme source. In some experiments, HEK293T cells were transfected with the respective sialidase cDNAs and their homogenates were used (24). Sialidase activity was measured with 4-methylumbelliferyl-neuraminic acid (4MU-NeuAc), GM3, sialyl-Le a , and sialyl-Le x (6 sugars, ganglioside-type, Wako Pure Industries, Osaka, Japan) as substrates.…”

Revisiting the Hansch–Fujita approach and development of a fundamental QSAR

“…These drugs have the potential to affect the activities of endogenous human NAs. 43,44) Thus, it is of great importance to examine differences in the binding mechanism between the influenza virus and human NAs with a series of sialic acid analogues. We selected influenza virus neuraminidase-1 (N1-NA) Hybrid (PCM/PB(GB)) 30…”