Isotetrandrine Reduces Astrocyte Cytotoxicity in Neuromyelitis Optica by Blocking the Binding of NMO-IgG to Aquaporin 4

Abstract

Objective: Neuromyelitis optica (NMO) is a severe neurological demyelinating autoimmune disease that affects the optic nerves and spinal cord with no cure and no FDA-approved therapy. Research over the last decade revealed that the binding of NMO-IgG to the water channel protein astrocyte aquaporin 4 (AQP4) might be the primary cause of NMO pathogenesis. The purpose of this study was to identify potential blockers of NMO-IgG and AQP4 binding. Methods: We developed a two-step screening platform consisting of a reporter cell-based high-throughput screen assay and a cell viability-based assay. Purified NMO-IgG from NMO patient serum and transfected Chinese hamster lung fibroblast V79 cells stably expressing human M23-AQP4 were used for primary screening of 40,000 small molecule fractions from 500 traditional Chinese herbs. Results: Thirty-six positive fractions were identified, of which 3 active fractions (at 50 μg/ml) were found to be from the same Chinese traditional herb Mahonia japonica (Thunb.). A bioactivity-guided method based on a primary screening assay for blocking activity led to the isolation of an active single natural compound, isotetrandrine, from the 3 fractions. Our immunofluorescence staining results showed that isotetrandrine can block NMO-IgG binding to AQP4 without affecting the expression and function of AQP4. It can also inhibit NMO-IgG binding to astrocyte AQP4 in NMO patient sera and block NMO-IgG-dependent complement-mediated cytotoxicity with the IC₅₀ at ∼3 μ<smlcap>M</smlcap>. Conclusions: The present study developed a cell-based high-throughput screen to identify small molecule inhibitors for NMO-IgG and AQP4 binding, and suggests a potential therapeutic value of isotetrandrine in NMO.

Aquaporins as Targets of Dietary Bioactive Phytocompounds

“…Isotetrandrine is a biscoclaurine alkaloid, a bioactive compound isolated from traditional Chinese herbs known for reducing the astrocyte cytotoxicity in the neurological autoimmune disorder such as neuromyelitis optica (NMO). This phytochemical was reported to be a small molecule inhibitor of NMO-IgG binding to AQP4 without impairing the expression and water channel activity of AQP4 (Sun et al, 2016 ).…”

Mining Therapeutic Efficacy from Treasure Chest of Biodiversity and Chemodiversity: Pharmacophylogeny of Ranunculales Medicinal Plants

“…(53) Alkaloids laudanosoline-1-O-xylopyranose, 6-O-methyl-laudanosoline-1-O-glucopyranoside, sinomenine, menisperine, laurifoline, magnoflorine and norsinoacutin were identifi ed in S. acutum. (54) Pyrrolo[2,1-a]isoquinoline and pyrrole alkaloids are isolated from S. acutum, (55) which are not found in other genera of Menispermaceae. The major difference between Sinomenium and Menispermum might lie in BBI, possibly due to the lack of BBI study on the former.…”

A critical review: traditional uses, phytochemistry, pharmacology and toxicology of Stephania tetrandra S. Moore (Fen Fang Ji)

“…Only two compounds, 9 and 52, have been evaluated for their antibacterial effects. Tetrandrine (9) (200.9, 401.9 or 803.8 lM) exhibited a synergistic effect against methicillin-resistant Staphylococcus aureus (MRSA) when combined with the multi-drug resistant (MDR)-efflux pump substrate ethidium bromide, causing a two to fourfold reduction in the minimum inhibitory concentration (MIC) of ethidium bromide against MRSA using a combined test (Lee et al 2011 Lai (2002), Sekiya et al (2004), Seow et al (1988), Lai et al (1999), Yun et al (2018), Yuan et al (2016), Lv et al (2015), Shan et al (2018), Hu et al (2012), Zhang et al (2018a, b, c, d), Zhang (2014), Sun et al (2016) Antifibrotic effects Antifibrotic effects in pulmonary disease . Though the compound exhibited potent inhibitory activity against S. aureus, the required dose of the two compounds was excessive in these studies, the experimental data not being relevant to clinical applications.…”

“…Neuromyelitis optica is a severe neurological demyelinating autoimmune disease that affects the optic nerves and the spinal cord. Isotetrandrine (27) at 100 lM has been shown to reduce astrocyte cytotoxicity in neuromyelitis optica by blocking the binding of neuromyelitis optica-immunoglobulin G (NMO-IgG) to aquaporin 4 (Sun et al 2016). However, the authors of this study did not perform comparisons using a positive control, as well as conducted only one too high concentration.…”