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Archive - Jan 1, 2019

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Why Olfactory Cilia Use Outward-Flowing Cl−, Not Inward-Flowing Na+, to Generate Current; Need for Consistent Response in Variable Environments & Tiny Volume of Cilia Are Key; Findings Relevant to Nerve-Ending Pathology in Neurodegenerative Disease

Imagine trying to figure out how something works when that something takes place in a space smaller than a femtoliter: one quadrillionith of a liter. Now, two scientists with a nose for solving mysteries have used a combination of mathematical modeling, electrophysiology, and computer simulations to explain how cells communicate effectively in highly constricted spaces such as the olfactory cilia, where odor detection takes place. The findings will inform future studies of cellular signaling and communication in the olfactory system and also in other confined spaces of the nervous system. Study co-author Johannes Reisert, PhD, a Monell Chemical Senses Center cell physiologist, comments, "Ion channels and how their currents change ion concentrations inside cells are notoriously difficult to study. Our modeling-based approach enables us to better understand, not only how olfaction works, but also the function of small nerve endings such as dendrites, where pathology is associated with many neurodegenerative diseases." In the study, published online on December 31, 2018 in PNAS, the scientists asked why olfactory receptor cells communicate with the brain using a fundamentally different series of electrical events than used by sensory cells in the visual or auditory systems. The article is titled “Ca2+-Activated Cl− Current Ensures Robust and Reliable Signal Amplification in Vertebrate Olfactory Receptor Neurons.” Olfaction begins when, in a process similar to a key fitting into a lock, an airborne chemical molecule travels through the nasal mucus to bind with an olfactory receptor embedded on the wall of a nerve cell within the nose. The olfactory receptors are located on cilia, elongated super-thin threadlike structures less than 0.000004 inches in diameter, which extend from the nerve cell into the mucus.

Chemotherapy Can Stimulate Release of Metastasis-Promoting Exosomes from Breast Cancer Cells; The Exosomes Release Their Contents in the Lungs; Monocyte Inhibitors May Block This Chemotherapy/Exosome-Associated Metastasis

Some patients with breast cancer receive chemotherapy before the tumor is removed with surgery. This approach, called “neoadjuvant” therapy, helps to reduce the size of the tumor to facilitate breast-conserving surgery, and can even eradicate the tumor, leaving few or no cancerous cells for the surgeon to remove. In those cases, the patients are very likely to remain cancer-free for life after surgery. But not all tumors shrink under chemotherapy. If the tumor resists neoadjuvant therapy, there can be a higher risk of developing metastatic disease, meaning that the tumor will recur in other organs, such as bones or lungs. This could be due to cancerous cells that resist chemotherapy and spread to other organs while the primary tumor is being treated. Now, an international team of scientists led by Dr. Michele De Palma, PhD, at EPFL (Ecole Polytechnique Fédérale De Lausann) in Switzerland, has shed new light into this process. Working with experimental tumor models, the researchers found that two chemotherapy drugs frequently used for patients, paclitaxel and doxorubicin, induce mammary tumors to release small vesicles called exosomes. Under chemotherapy, the exosomes contain the protein annexin-A6, which is not present in the exosomes released from untreated tumors. "It seems that loading of annexin-A6 into exosomes is significantly enhanced in response to chemotherapy," explains Ioanna Keklikoglou, PhD, first author of the study. After being released from a chemotherapy-treated tumor, the exosomes circulate in the blood. Upon reaching the lung, the exosomes release their content, including annexin-A6. This stimulates the lung cells to release another protein, CCL2, which attracts immune cells called monocytes.