NS-398-induced membrane stiffening as a biophysical factor affecting memory-related processes

The cell membrane is a structure composed of lipids, proteins and signaling molecules. As such, it is thermodynamically active and maintains cellular integrity. The appropriate balance of polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA) and arachidonic acid (AA), modulates neuronal membrane fluidity. At the same time, it influences long-term potentiation (LTP) and memory function. Cyclooxygenase-2 (COX-2) is an enzyme responsible for prostaglandin synthesis. It acts via the AA cascade pathway. In the clinic, COX-2 inhibitors are used as adjunctive therapies in depression, and their effects on cognitive function have been reported; however, the mechanism underlying these changes remains unclear. We hypothesize that NS398, a selective COX-2 inhibitor, alters memory performance by modulating biophysical properties of membranes. To test this, we performed a modified Barnes maze (MBM) test in mice, measured the elastic modulus of the prefrontal cortex with atomic force microscopy (AFM), and analyzed Langmuir pressure-area isotherms in a DPPC (dipalmitoylphosphatidylcholine) model system. Treatment with NS398 significantly stiffened the membrane of the prefrontal cortex. We observed a correlation with changes in memory function. Langmuir isotherm analysis and quantitative AFM studies confirmed these results. We found a more than tenfold increase in membrane stiffness and consistent changes in its compressibility. CONCLUSION: Our findings demonstrate that COX-2 inhibition increases cell membrane stiffness, implicating membrane mechanics as a novel link between biochemical signaling and cognitive functions.