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Hyperammonemia leading to astrocyte swelling and cerebral edema in combination with neuroinflammation including microglia activation, mainly contribute to the pathogenesis of HE. However, little is known about microglia and their inflammatory response, as well as their influence on astrocytic channels and astrocyte swelling under hyperammonemia.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To investigate the effects of ammonia on the microglial activation and morphology in different set-ups of an in vitro astrocyte-microglia co-culture model. Further, potential effects on glial viability, connexin 43 (Cx43) and aquaporin 4 (AQP4) expression were tested.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Primary rat glial co-cultures of astrocytes containing 5% (M5, representing \"physiological\" conditions) or 30% (M30, representing \"pathological\" conditions) of microglia were incubated with 3\u00a0mM, 5\u00a0mM, 10\u00a0mM and 20\u00a0mM ammonium chloride (NH4Cl) for 6\u00a0h and 24\u00a0h in order to mimic the conditions of HE. An MTT assay was performed to measure the viability, proliferation and cytotoxicity of cells. The microglial phenotypes were analyzed by immunocytochemistry. The expression of Cx43 and AQP4 were quantified by immunoblot analysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>A significant reduction of glial viability was observed in M30 co-cultures after incubation with 20\u00a0mM NH4Cl for 6\u00a0h, whereas in M5 co-cultures the viability remained unchanged. Microglial activation was detected by immunocytochemistry after incubation with 3\u00a0mM, 5\u00a0mM and 10\u00a0mM NH4Cl for 6\u00a0h and 24\u00a0h in M5 as well as in M30 co-cultures. The Cx43 expression was slightly increased in M30 co-cultures after 6\u00a0h incubation with 5\u00a0mM NH4Cl. Also, the AQP4 expression was slightly increased only in M5 co-cultures treated with 10\u00a0mM NH4Cl for 6\u00a0h. Under the other conditions, Cx43 and AQP4 expression was not affected by NH4Cl.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>The novel aspect of our study was the significant microglial activation and decrease of viability after NH4Cl incubation in different set-ups of an in vitro astrocyte-microglia co-culture model, contributing to better understanding of pathophysiological mechanisms of HE. Hyperammonemia led to limited effects on Cx43 and AQP4 expression, the relevance of these minimal changes should be viewed with caution.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s12868-021-00628-1","type":"journal-article","created":{"date-parts":[[2021,3,25]],"date-time":"2021-03-25T09:05:37Z","timestamp":1616663137000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Ammonia induced microglia activation was associated with limited effects on connexin 43 and aquaporin 4 expression in an astrocyte-microglia co-culture model"],"prefix":"10.1186","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3930-8056","authenticated-orcid":false,"given":"Fatme Seval","family":"Ismail","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Timo Jendrik","family":"Faustmann","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Franco","family":"Corvace","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anamariya","family":"Tsvetanova","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zahra","family":"Moinfar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pedro M.","family":"Faustmann","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2021,3,25]]},"reference":[{"key":"628_CR1","doi-asserted-by":"publisher","first-page":"845","DOI":"10.1001\/archneur.1989.00520440027016","volume":"46","author":"RA Brumback","year":"1989","unstructured":"Brumback RA, Lapham LW. 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