Redistribution of ASIC1a channels triggered by IL-6: Potential role of ASIC1a in neuroinflammation.

Cytokines, particularly IL-6, play a crucial role in modulating immune responses in the central nervous system (CNS). Elevated IL-6 levels have been observed in neuroinflammatory conditions, as well as in the sera and brains of patients with neurodegenerative diseases such as Parkinson's, Huntington's, Multiple Sclerosis, and Alzheimer's. Additionally, alterations in regional brain pH have been noted in these conditions. Acid-sensing ion channels (ASICs), including ASIC1a, activated by low pH levels, are highly abundant in the CNS and have recently been associated with various neurological disorders. Our study examined the impact of IL-6 on ASIC1a channels in cell cultures, demonstrating IL-6-induced the redistribution of cytosolic ASIC1a channels to the cell membrane. This redistribution was accompanied by increased ASIC1a current amplitude upon activation, as well as elevated levels of phosphorylated CaMKII and ERK kinases. Additionally, we observed posttranslational modifications on the ASIC1a channel itself. These findings provide insight into a potential link between inflammatory processes and neurodegenerative mechanisms, highlighting ASIC1a channels as promising therapeutic targets in these conditions.

Dynamic Distribution of ASIC1a Channels and Other Proteins within Cells Detected through Fractionation.

Proteins in eukaryotic cells reside in different cell compartments. Many studies require the specific localization of proteins and the detection of any dynamic changes in intracellular protein distribution. There are several methods available for this purpose that rely on the fractionation of the different cell compartments. Fractionation protocols have evolved since the first use of a centrifuge to isolate organelles. In this study, we described a simple method that involves the use of a tabletop centrifuge and different detergents to obtain cell fractions enriched in cytosolic (Cyt), plasma membrane (PM), membranous organelle (MO), and nuclear (Nu) proteins and identify the proteins in each fraction. This method serves to identify transmembrane proteins such as channel subunits as well as PM-embedded or weakly associated proteins. This protocol uses a minute amount of cell material and typical equipment present in laboratories, and it takes approximately 3 h. The process was validated using endogenous and exogenous proteins expressed in the HEK293T cell line that were targeted to each compartment. Using a specific stimulus as a trigger, we showed and quantified the shuttling of a protein channel (ASIC1a, acid sensing ion channel) from the MO fraction to the PM fraction and the shuttling of a kinase from a cytosolic location to a nuclear location.

Molecular and microstructural biomarkers of neuroplasticity in neurodegenerative disorders through preclinical and diffusion magnetic resonance imaging studies.

Advances in the understanding of genetic and molecular mechanisms and imaging technologies have opened a new window of research possibilities to address dynamic processes associated with neuroplasticity in physiologically intact models of neurodegenerative diseases. This review aims to: (i) establish the most relevant molecular mechanisms, as well as cellular and structural biomarkers in the study of neuroplasticity; (ii) introduce different neurodegenerative diseases in animal models that contribute to our knowledge of neuroplasticity; and (iii) illustrate the capabilities and limitations of current diffusion magnetic resonance imaging techniques to study cortical plasticity, as well as the use of alternative diffusion models.

Upregulation of ASIC1a channels in an in vitro model of Fabry disease.

Neuropathic pain is one of the key features of the classical phenotype of Fabry disease (FD). Acid sensing ion channels (ASICs) are H+-gated cation channels, which belong to the epithelial sodium channel/DeGenerin superfamily, sensitive to the diuretic drug Amiloride. Molecular cloning has identified several distinct ASIC subunits. In particular the ASIC1a subunit has been associated to pain and its upregulation has been documented in animal models of pain. We analyzed the expression of ASIC1a channels in cellular models that mimic the accumulation of glycosphingolipids in FD (FD-GLs) like Gb3, and LysoGb3. We used mouse primary neurons from brain cortex and hippocampus -supraspinal structures that accumulate FD-GLs-, as well as HEK293 cells. Incubation with Gb3, lysoGb3 and the inhibitor (1-deoxy-galactonojirymicin, DJG) of the enzyme α-galactosidase A (Gla) lead to the upregulation of ASIC1a channels. In addition, activation of ASIC1a results in the activation of the MAPK ERK pathway, a signaling pathway associated with pain. Moreover, accumulation of glycosphingolipids results in activation of ERK, an effect that was prevented by blocking ASIC1a channels with the specific blocker Psalmotoxin. Our results suggest that FD-GLs accumulation and triggering of the ERK pathway via ASIC channels might be involved in the mechanism responsible for pain in FD, thus providing a new therapeutic target for pain relief treatment.

Diffusion Tensor Imaging in Preclinical and Human Studies of Huntington's Disease: What Have we Learned so Far?

BACKGROUND: Huntington's Disease is an irreversible neurodegenerative disease characterized by the progressive deterioration of specific brain nerve cells. The current evaluation of cellular and physiological events in patients with HD relies on the development of transgenic animal models. To explore such events in vivo, diffusion tensor imaging has been developed to examine the early macro and microstructural changes in brain tissue. However, the gap in diffusion tensor imaging findings between animal models and clinical studies and the lack of microstructural confirmation by histological methods has questioned the validity of this method. OBJECTIVE: This review explores white and grey matter ultrastructural changes associated to diffusion tensor imaging, as well as similarities and differences between preclinical and clinical Huntington's Disease studies. METHODS: A comprehensive review of the literature using online-resources was performed (Pub- Med search). RESULTS: Similar changes in fractional anisotropy as well as axial, radial and mean diffusivities were observed in white matter tracts across clinical and animal studies. However, comparative diffusion alterations in different grey matter structures were inconsistent between clinical and animal studies. CONCLUSION: Diffusion tensor imaging can be related to specific structural anomalies in specific cellular populations. However, some differences between animal and clinical studies could derive from the contrasting neuroanatomy or connectivity across species. Such differences should be considered before generalizing preclinical results into the clinical practice. Moreover, current limitations of this technique to accurately represent complex multicellular events at the single micro scale are real. Future work applying complex diffusion models should be considered.