Pathways

Vinblastine (also named Velban) is a natural alkaloid isolated from Vinca rosea, originally from Catharanthus (vinca) roseus. Vinblastine is used as chemotherapy medication such as an antimitotic agent. It is used as a treatment of breast cancer, testicular cancer, neuroblastoma, Hodgkin's and non-Hodgkins lymphoma, mycosis fungoides, histiocytosis and Kaposi's sarcoma. Its antitumor activity is thought to be due primarly to inhibition of mitosis at metaphase through interaction its interaction with tubulin (microtubules). Vinblastine binds specifically to microtubular proteins (tubulin) of the mitotic spindle, leading to crystallization of the microtubules (not dynamic anymore). In consequence, there is a mitotic arrest leading to the cell death. The disarray of microtubules induces two proteins; cellular tumor antigen p53 and cyclin dependent kinase inhibitor p21. The latter protein works to inhibit cyclin dependent kinases in the cell, which disrupt the phosphorylation of the apoptosis inhibitor Bcl-2. Bcl-2 suppresses apoptosis by regulating permeability of the mitochondrial membrane, but is unable to do so due to the interrupted phosphorylation. The former protein, p53, acts on BAK and BAX to enact conformational changes, creating pores in the mitochondrial membrane that allow the exit of cytochrome c. Cytochrome c further activates capsases in the cell, which cleave essential cellular proteins. In this way, p53 and p21 work alongside each other to promote apoptosis and terminate unhealthy cells.

Vinblastine (also named Velban) is a natural alkaloid isolated from the leaves of the Catharanthus roseus (commonly known as the Madagascar periwinkle). Vinblastine are used as chemotherapy medication such as an antimitotic anticancer agent. The mechanism of vinblastine is the inhibition of microtubule dynamics that would cause mitotic arrest and eventual cell death. As a microtubule destabilizing agent, Vinblastine stimulates mitotic spindle destruction and microtubule depolymerization at high concentrations. At lower clinically relevant concentrations, vinblastine can block mitotic progression. Unlike the taxanes, which bind poorly to soluble tubulin, vinblastine can bind both soluble and microtubule-associated tubulin. To be able stabilizing the kinetics of microtule, vinblastine rapidly and reversibly bind to soluble tubulin which can increase the affinity of tublin by the induction of conformational changes of tubulin. Vinblastine binds to β-tubulin subunits at the positive end of microtubules at a region called the _Vinca_-binding domain. Binding between vinblastine and solubale tubulin decreases the rate of microtubule dynamics (lengthening and shortening) and increases the duration of attenuated state of microtubules. Therefore, the proper assembly of the mitotic spindle could be prevented; and the tension at the kinetochores of the chromosomes could be reduced. Subsequently, chromosomes can not progress to the spindle equator at the spindle poles. Progression from metaphase to anaphase is blocked and cells enter a state of mitotic arrest. The cells may then undergo one of several fates. The tetraploid cell may undergo unequal cell division producing aneuploid daughter cells. Alternatively, it may exit the cell cycle without undergoing cell division, a process termed mitotic slippage or adaptation. These cells may continue progressing through the cell cycle as tetraploid cells (Adaptation I), may exit G1 phase and undergo apoptosis or senescence (Adaption II), or may escape to G1 and undergo apoptosis during interphase (Adaptation III). Another possibility is cell death during mitotic arrest. Alternatively, mitotic catastrophe may occur and cause cell death. Vinca alkaloids are also thought to increase apoptosis by increasing concentrations of p53 (cellular tumor antigen p53) and p21 (cyclin-dependent kinase inhibitor 1) and by inhibiting Bcl-2 activity. Increasing concentrations of p53 and p21 lead to changes in protein kinase activity. Phosphorylation of Bcl-2 subsequently inhibits the formation Bcl-2-BAX heterodimers. This results in decreased anti-apoptotic activity. One way in which cells have developed resistance against the vinca alkaloids is by drug efflux. Drug efflux is mediated by a number of multidrug resistant transporters as depicted in this pathway.

Metabolites of Vilazodone are predicted with biotransformer.

Vilazodone selectively inhibits serotonin reuptake in the central nervous system as well as acting as a partial agonist of 5HT-1A receptors. The exact mechanism for how these effects translate to its antidepressant effects are not known though there is an association between these effects and anti-depressive activity.