The Rab11-regulated endocytic pathway and BDNF/TrkB signaling: Roles in plasticity changes and neurodegenerative diseases.

Neurons are highly polarized cells that rely on the intracellular transport of organelles. This process is regulated by molecular motors such as dynein and kinesins and the Rab family of monomeric GTPases that together help move cargo along microtubules in dendrites, somas, and axons. Rab5-Rab11 GTPases regulate receptor trafficking along early-recycling endosomes, which is a process that determines the intracellular signaling output of different signaling pathways, including those triggered by BDNF binding to its tyrosine kinase receptor TrkB. BDNF is a well-recognized neurotrophic factor that regulates experience-dependent plasticity in different circuits in the brain. The internalization of the BDNF/TrkB complex results in signaling endosomes that allow local signaling in dendrites and presynaptic terminals, nuclear signaling in somas and dynein-mediated long-distance signaling from axons to cell bodies. In this review, we briefly discuss the organization of the endocytic pathway and how Rab11-recycling endosomes interact with other endomembrane systems. We further expand upon the roles of the Rab11-recycling pathway in neuronal plasticity. Then, we discuss the BDNF/TrkB signaling pathways and their functional relationships with the postendocytic trafficking of BDNF, including axonal transport, emphasizing the role of BDNF signaling endosomes, particularly Rab5-Rab11 endosomes, in neuronal plasticity. Finally, we discuss the evidence indicating that the dysfunction of the early-recycling pathway impairs BDNF signaling, contributing to several neurodegenerative diseases.

Antineoplastic activity of rinvanil and phenylacetylrinvanil in leukaemia cell lines.

In the search for novel chemotherapeutic agents for cancer treatment, capsaicin has been shown to inhibit proliferation and induce apoptosis in various types of cancer cell line, including leukaemia cell lines. The capsaicin analogues, rinvanil and phenylacetylrinvanil (PhAR), share a binding affinity for vanilloid receptors and may have biological activities similar to capsaicin; however, their anticancer potential has not yet been reported. This study analyses the antineoplastic activities of rinvanil and PhAR in leukaemia versus normal cells. P388, J774 and WEHI-3 leukaemia cell lines, as well as mouse bone marrow mononuclear cells, were cultured with varying concentrations of rinvanil and PhAR. Following this, proliferation and apoptosis were determined by the sulforhodamine B (SRB) assay and DNA ladder. Cultured leukaemia cell lines and mouse bone marrow mononuclear cells demonstrated a dose-dependent inhibition of proliferation, while non-diseased cells were less sensitive to the cytotoxic effect of capsaicin, rinvanil and PhAR. Rinvanil and PhAR also induced apoptosis in leukaemia cell lines but not in bone marrow. Given the lower IC50 values for apoptosis induction in leukaemia cells compared with that of normal cells, PhAR is a promising selective anticancer agent.