Deep insights into the mechanism of isorhamnetin's anti-motion sickness effect based on photoshoproteomics

Isorhamnetin has recently been found to exhibit a remarkable anti-motion sickness effect, yet the underlying mechanism is still unclear. Herein, network pharmacology was employed to conduct a preliminary analysis on the possible biological processes involved. Results showed that common targets were localized in membranes, mitochondria, and glutamatergic synapses. In particular, protein phosphorylation, protein serine/threonine/tyrosinase activity and signal transduction might play a role in isorhamnetin's anti-motion sickness effect. Thus, mice phosphoproteomics analysis was further performed to explore the phosphorylated protein changes in the motion sickness process. Results showed that differentially phosphorylated proteins have an effect on postsynaptic density, glutamatergic synapses and other sites and are involved in various neurodegenerative disease pathways, endocytic pathways, cAMP signaling pathways and MAPK signaling pathways. Two key differentially phosphorylated proteins in glutamatergic synapses, namely, DLGAP and EPS8, might play key roles in isorhamnetin's anti-motion sickness process. The final molecular experimental verification results from qRT-PCR and western blot analyses indicated that isorhamnetin firstly regulates glutamatergic synapses and then reduces the excitability of the vestibular nucleus through inhibiting the NMDAR1/CaMKII/CREB signaling pathway, ultimately alleviating a series of symptoms of motion sickness in mice. The findings of this study provide valuable insights and a useful theoretical basis for the application of isorhamnetin as a new anti-motion sickness food ingredient.