Umbelliferone and scopoletin target tyrosine kinases on fibroblast-like synoviocytes to block NF-κB signaling to combat rheumatoid arthritis.

Rheumatoid arthritis (RA) is a complex autoimmune condition primarily affecting synovial joints, which targeted synthetic drugs have damaging safety issues. Saussurea laniceps, a reputed anti-rheumatic medicinal herb, is an excellent place to start looking for natural products as safe, effective, targeted therapeutics for RA. Via biomimetic ultrafiltration, umbelliferone and scopoletin were screened as two anti-rheumatic candidates with the highest specific affinities towards the membrane proteomes of rheumatic fibroblast-like synoviocytes (FLS), the pivotal effector cells in RA. In vitro assays confirmed that the two compounds, to varying extents, inhibited RA-FLS proliferation, migration, invasion, and NF-κB signaling. Network pharmacology analysis and molecular docking analysis jointly revealed that umbelliferone and scopoletin act on multiple targets, mostly tyrosine kinases, in combating RA. Taken together, our present study identified umbelliferone and scopoletin as two major anti-rheumatic components from SL that may bind and inhibit tyrosine kinases and subsequently inactivate NF-κB in RA-FLSs. Our integrated drug discovery strategy could be valuable in finding other multi-target bioactive compounds from complex matrices for treating multifactorial diseases.

Critical role of s465 in protein kinase C-increased rat glutamate transporter type 3 activity.

Glutamate transporters, also called excitatory amino acid transporters (EAATs), uptake extracellular glutamate and regulate neurotransmission. Activation of protein kinase C (PKC) increases the activity of EAAT type 3 (EAAT3), the major neuronal EAAT. We designed this study to determine which amino acid residue(s) in EAAT3 may be involved in this PKC effect. Selective potential PKC phosphorylation sites were mutated. These EAAT3 mutants were expressed in the Xenopus oocytes. Phorbol 12-myristate 13-acetate, a PKC activator, significantly increased wild-type EAAT3 activity. Mutation of serine 465 to alanine or aspartic acid, but not the mutation of threonine 5 to alanine, abolished PKC-increased EAAT3 activity. Our results suggest a critical role of serine 465 in the increased EAAT3 activity by PKC activation.