Microglial activation involves both fragmentation of the mitochondrial network and changes in cellular Ca2+ homeostasis, but possible modifications in mitochondrial calcium uptake have never been described in this context. Here we report that activated microglial BV-2 cells have impaired mitochondrial calcium uptake, including lower calcium retention capacity and calcium uptake rates. These changes were not dependent on altered expression of the mitochondrial calcium uniporter. Respiratory capacity and the inner membrane potential, key determinants of mitochondrial calcium uptake, are both decreased in activated microglial BV-2 cells. Modified mitochondrial calcium uptake correlates with impaired cellular calcium signaling, including reduced ER calcium stores, and decreased replenishment by store operated calcium entry (SOCE). Induction of mitochondrial fragmentation through Mfn2 knockdown in control cells mimicked this effect, while inhibiting LPS-induced mitochondrial fragmentation by a dominant negative form of Drp1 prevented it. Overall, our results show that mitochondrial fragmentation induced by LPS promotes altered Ca2+ homeostasis in microglial cells, a new aspect of microglial activation that could be a key feature in the inflammatory role of these cells.
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The authors acknowledge Sirlei Mendes de Oliveira and Camille Caldeira da Silva (Universidade de São Paulo) for their outstanding technical support. The graphical abstract was created from adapted figures and templates available at Servier Medical Art by Servier (https://smart.servier.com) under a Creative Commons Attribution 3.0 Unported License.
This work was funded by grants #2020/06970–5 and #2013/07937–8 from the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Centro de Pesquisa, Inovação e Difusão de Processos Redox em Biomedicina (CEPID Redoxoma), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). O.R.P.Jr. is supported by FAPESP grant #2018/21487–9. V.M.R. is supported by FAPESP grant #2019/18402–4. J.V.C.-C. is supported by FAPESP grants #2017/14713–0 and #2019/22178–2.
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Pereira, O.R., Ramos, V.M., Cabral-Costa, J.V. et al. Changes in mitochondrial morphology modulate LPS-induced loss of calcium homeostasis in BV-2 microglial cells. J Bioenerg Biomembr (2021). https://doi.org/10.1007/s10863-021-09878-4
- Calcium handling
- Mitochondrial morphology