The carotid body is a major peripheral chemoreceptor that senses changes in arterial blood oxygen, carbon dioxide, and pH, what is important for regulation of breathing and cardiovascular function. The mechanisms by which the carotid body senses O2 and CO2 are well known; conversely, the mechanisms by which it senses pH variations are almost unknown. Here we used immunohistochemistry to investigate how the human carotid body contributes to the detection acidosis analyzing whether it expresses acid-sensing ion channels (ASIC) ion channels, and to know if these channels are in the cells chemosensory glomic cells or in the afferent nerves. ASIC1, ASIC2 and ASIC3, and to a much lesser extent ASIC4, immunoreactivity was detected in subpopulations of type I glomus cells, as well as in the nerves of the carotid body. In addition, immunoreactivity was found for all ASIC subunits in neurons of the petrosal and superior cervical sympathetic ganglia, where afferent and efferent neurons are located, respectively, innervating the carotid body. This study reports for the fist time the occurrence of ASIC proteins in the human carotid body, demonstrating that they are present in glomus chemosensory cells (ASIC1 < ASIC2 > ASIC3 > ASIC4) and nerves, presumably both afferent an efferent supplying the organ. These results suggest that the detection of acidosis by the carotid body can be mediated by ASIC ion channels present in the type I glomus cells or directly by sensory nerve fibers.

In the last decade a group of Ca2+ channels called Piezo were discovered, demonstrating a decisive role in the cellular response to mechanical stimuli and being essential in the biological behaviour of cells regarding the extracellular compartment. Several investigations have suggested a potential role in carcinogenesis with a tumor supressor role in some cases, but increased expression in several high grade neoplasms. Regarding Piezo2 expression in mammary gland neoplasms, early results suggested a protective role of Piezo2, but posterior works resulted in a relationship between Piezo2 expression and the highly-aggressive triple negative phenotype of breast carcinoma. A cohort of 125 patients with clinical follow up was chosen to study Piezo2 expression and clarify its clinical implications, using the same immunohistochemical valuation performed for other breast carcinoma parameters. Fisher exact was chosen to identify potential relationships between the different variables. A significant association was found with the Ki67 proliferation index, but not with mitoses. The tendency of most proliferative tumors was to have a diminished score for Piezo2. A similar association was found between Piezo2 expression and perineurial invasion.