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The potassium channel KCa3.1 constitutes a pharmacological target for astrogliosis associated with ischemia stroke.

ABSTRACT: Reactive astrogliosis is one of the significantly pathological features in ischemic stroke accompanied with changes in gene expression, morphology, and proliferation. KCa3.1 was involved in TGF-?-induced astrogliosis in vitro and also contributed to astrogliosis-mediated neuroinflammation in neurodegeneration disease.Wild type mice and KCa3.1-/- mice were subjected to permanent middle cerebral artery occlusion (pMCAO) to evaluate the infarct areas by 2,3,5-triphenyltetrazolium hydrochloride staining and neurological deficit. KCa3.1 channels expression and cell localization in the brain of pMCAO mice model were measured by immunoblotting and immunostaining. Glia activation and neuron loss was measured by immunostaining. DiBAC4 (3) and Fluo-4AM were used to measure membrane potential and cytosolic Ca2+ level in oxygen-glucose deprivation induced reactive astrocytes in vitro.Immunohistochemistry on pMCAO mice infarcts showed strong upregulation of KCa3.1 immunoreactivity in reactive astrogliosis. KCa3.1-/- mice exhibited significantly smaller infarct areas on pMCAO and improved neurological deficit. Both activated gliosis and neuronal loss were attenuated in KCa3.1-/- pMCAO mice. In the primary cultured astrocytes, the expressions of KCa3.1 and TRPV4 were increased associated with upregulation of astrogliosis marker GFAP induced by oxygen-glucose deprivation. The activation of KCa3.1 hyperpolarized membrane potential and, by promoting the driving force for calcium, induced calcium entry through TRPV4, a cation channel of the transient receptor potential family. Double-labeled staining showed that KCa3.1 and TRPV4 channels co-localized in astrocytes. Blockade of KCa3.1 or TRPV4 inhibited the phenotype switch of reactive astrogliosis.Our data suggested that KCa3.1 inhibition might represent a promising therapeutic strategy for ischemia stroke.

SUBMITTER: Yi M

PROVIDER: S-EPMC5644250 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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The potassium channel KCa3.1 constitutes a pharmacological target for astrogliosis associated with ischemia stroke.

Yi Mengni M Wei Tianjiao T Wang Yanxia Y Lu Qin Q Chen Gaoxian G Gao Xiaoling X Geller Herbert M HM Chen Hongzhuan H Yu Zhihua Z

Journal of neuroinflammation 20171016 1

<h4>Background</h4>Reactive astrogliosis is one of the significantly pathological features in ischemic stroke accompanied with changes in gene expression, morphology, and proliferation. KCa3.1 was involved in TGF-β-induced astrogliosis in vitro and also contributed to astrogliosis-mediated neuroinflammation in neurodegeneration disease.<h4>Methods</h4>Wild type mice and KCa3.1<sup>-/-</sup> mice were subjected to permanent middle cerebral artery occlusion (pMCAO) to evaluate the infarct areas by ...[more]

PMID: 29037241

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Project description:Ion channels are non-conventional, druggable oncological targets. The intermediate-conductance calcium-dependent potassium channel (KCa3.1) is highly expressed in the plasma membrane and in the inner mitochondrial membrane (mitoKCa3.1) of various cancer cell lines. The role mitoKCa3.1 plays in cancer cells is still undefined. Here we report the synthesis and characterization of two mitochondria-targeted novel derivatives of a high-affinity KCa3.1 antagonist, TRAM-34, which retain the ability to block channel activity. The effects of these drugs were tested in melanoma, pancreatic ductal adenocarcinoma and breast cancer lines, as well as in vivo in two orthotopic models. We show that the mitochondria-targeted TRAM-34 derivatives induce release of mitochondrial reactive oxygen species, rapid depolarization of the mitochondrial membrane, fragmentation of the mitochondrial network. They trigger cancer cell death with an EC50 in the µM range, depending on channel expression. In contrast, inhibition of the plasma membrane KCa3.1 by membrane-impermeant Maurotoxin is without effect, indicating a specific role of mitoKCa3.1 in determining cell fate. At sub-lethal concentrations, pharmacological targeting of mitoKCa3.1 significantly reduced cancer cell migration by enhancing production of mitochondrial reactive oxygen species and nuclear factor-κB (NF-κB) activation, and by downregulating expression of Bcl-2 Nineteen kD-Interacting Protein (BNIP-3) and of Rho GTPase CDC-42. This signaling cascade finally leads to cytoskeletal reorganization and impaired migration. Overexpression of BNIP-3 or pharmacological modulation of NF-κB and CDC-42 prevented the migration-reducing effect of mitoTRAM-34. In orthotopic models of melanoma and pancreatic ductal adenocarcinoma, the tumors at sacrifice were 60% smaller in treated versus untreated animals. Metastasis of melanoma cells to lymph nodes was also drastically reduced. No signs of toxicity were observed. In summary, our results identify mitochondrial KCa3.1 as an unexpected player in cancer cell migration and show that its pharmacological targeting is efficient against both tumor growth and metastatic spread in vivo.

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The potassium channel KCa3.1 constitutes a pharmacological target for astrogliosis associated with ischemia stroke.

Publications

The potassium channel KCa3.1 constitutes a pharmacological target for astrogliosis associated with ischemia stroke.

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