The interactions of phenytoin and its binding site in DI‐S6 segment of Na+ channel voltage‐gated peptide by NMR spectroscopy and molecular modeling study

Abstract: Nuclear magnetic resonance (NMR) spectra of a model peptide (BL‐DIS6), in the presence of anticonvulsant diphenyl drug, phenytoin (DPH), were measured to obtain the interactions between the selected drug and the model peptide. BL‐DIS6's sequence corresponds to the S6 segment in domain I of rat brain type IIA Na⁺‐channel. NMR studies have demonstrated that the magnitude of the chemical shifts of amide‐ and α‐protons can be used as a measurement of the complex stability and binding site of the peptide. Our NMR results propose a 3₁₀‐helical structure for BL‐DIS6, and suggest a binding cavity for DPH that involves the hydrophobic particles of residues Ans‐7, Leu‐8, Val‐11, and Val‐12. Furthermore, molecular modeling was performed to provide a possible complex conformation that the phenyl portion of DPH is accommodated in the proximity of the C‐terminal residues Ala‐11 and Val‐12, and simultaneously the heterocyclic amine ring of DPH is perching at the residue Asn‐7 periphery and stabilizing the phenyl portion deep insertion into the peptide.     

Vascular modulation through exercise improves chemotherapy efficacy in Ewing sarcoma

Recent studies in mouse models of cancer have shown that exercise improves tumor vascular function, thereby improving chemotherapy delivery and efficacy. However, the mechanisms underlying this improvement remain unclear and the effect of exercise on Ewing sarcoma (ES), a pediatric bone and soft tissue cancer, is unknown. The effect of exercise on tumor vascular hyperpermeability, which inversely correlates with drug delivery to the tumor, has also not been evaluated. We hypothesized that exercise improves chemotherapy efficacy by enhancing its delivery through improving tumor vascular permeability. We treated ES‐bearing mice with doxorubicin with or without moderate treadmill exercise. Exercise did not significantly alter ES tumor vessel morphology. However, compared to control mice, tumors of exercised mice had significantly reduced hyperpermeability, significantly decreased hypoxia, and higher doxorubicin penetration. Compared to doxorubicin alone, doxorubicin plus exercise inhibited tumor growth more efficiently. We evaluated endothelial cell sphingosine‐1‐phosphate receptors 1 and 2 (S1PR1 and S1PR2) as potential mediators of the improved vascular permeability and increased function afforded by exercise. Relative to tumors from control mice, vessels in tumors from exercised mice had increased S1PR1 and decreased S1PR2 expression. Our results support a model in which exercise remodels ES vasculature to reduce vessel hyperpermeability, potentially via modulation of S1PR1 and S1PR2, thereby improving doxorubicin delivery and inhibiting tumor growth more than doxorubicin alone does. Our data suggest moderate aerobic exercise should be tested in clinical trials as a potentially useful adjuvant to standard chemotherapy for patients with ES.