Modulation of HMGB1 in reactive and irresponsive microglia treated with amyloid-β peptide

• Autor(a) principal: Nunes, Maria Carlos Cortegaça da Cruz
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/20581
• topic: Alzheimer’s disease; Amyloid-β peptide; Inflammation; Reactive and aged microglia; High mobility group box 1 modulation; Microglial function and dysfunction; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Neuroinflammation is associated with microglia reactivity in Alzheimer’s disease (AD) in the presence of amyloid-β (Aβ) peptide. Interestingly, expression and activation of the alarmin high mobility group box 1 (HMGB1) were recently associated with neuroinflammation in the aged brain and noticed to contribute to AD pathology. Recent results from our group indicate that Aβ upregulates HMGB1 mRNA in a culture model of reactive microglial cells. Here we aimed to assess the effects of modulating HMGB1 gene expression in young/reactive and aged/irresponsive microglia, when stimulated by Aβ. Therefore, mixed glial cultures were obtained from CD1 mice pups. Microglia were isolated, maintained for 3 (young) or 16 (aged) days in vitro (DIV) and transiently transfected to silence (si) or overexpress (p) HMGB1, respectively. Cells were then treated (or not) with a mixture of Aβ species (1000 nM). We evaluated: autophagy (LC3II/I and Beclin-1); phagocytosis (MFG-E8); phenotypic markers of pro-inflammatory (TLR2/TLR4/NF-kB signalling pathway, NLRP3-inflammasome/IL-18 complex, TNF-α, iNOS and MHCII) or anti-inflammatory (IL-10 and Arginase-1, CX3CR1) stages; inflamma-miRNAs (miR-155, miR-124 and miR-146a); and senescence. Aβ induced HMGB1 expression in 3 DIV/young microglia and promoted autophagy, M1 polarization, as well as senescence, while reducing MFG-E8-associated phagocytosis. Efficient siHMGB1 abrogated all these effects, with exception of NLRP3 mRNA upsurge. Contrarily, Aβ couldn’t trigger HMGB1 upregulation in 16DIV/aged microglia, only achieved in pHMGB1-treated samples. pHMGB1 diminished senescence in Aβ-challenged cells and increased the expression of pro- and anti-inflammatory markers, even in the absence of Aβ challenge. Overall, our data suggest that siHMGB1 protects young microglia from excessive activation without compromising their responsiveness, while pHMGB1 allows aged microglia to regain a reactive profile. Therefore, selective modulation of HMGB1 appears essential to preserve microglia’s key functions, supporting a potential therapeutic application in AD with advantages over conventional broad effect anti-inflammatory agents.