Betaine, an Organic Osmolyte Effectively Counteracts the Deleterious Effect of Diclofenac on Protein Structure and Stability

Understanding physical chemistry underlying drug-protein interaction is essential to devise guidelines for the synthesis of target-oriented drugs. In the present study, the effects of the non-steroidal anti-inflammatory drug (NSAID), diclofenac sodium (DCF) on the stability and structure of Bovine Pancreatic Ribonuclease-A (RNase-A) taken as model protein has been examined by thermal stability, circular dichroism, intrinsic fluorescence, and docking studies. Since drug-protein interaction is an important pharmacokinetic parameter of a drug, it was deemed significant to study the effects of DCF on protein structure and stability. When the thermodynamic parameters were assessed, DCF was observed to destabilized RNase-A in terms of T_m and \(\Delta G_{{\text{D}}}^{^\circ }\) while the addition of osmolytes stabilized the protein. In the presence of DCF and osmolyte, a change in the tertiary structure but not in the secondary structure of the protein was observed. The fluorescence study showed a decrease in the fluorescence intensity confirming the quenching of RNase-A fluorescence by DCF and osmolytes. Molecular docking studies revealed the involvement of hydrogen bonds and Van der Waals in RNase-A-DCF interaction. The activity of this enzyme RNAse-A is decreased in presence of DCF while osmolyte helps bring back the activity by increasing k_cat and decreasing K_m values. This study will provide the platform for the use of combinatorial therapy of DCF with osmolytes to offsets the harmful effects of DCF.