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Microglia modulate Ang II induced neuronal activity and neuroinflammation
Author(s) -
Santisteban Monica M,
Zubcevic Jasenka,
Febo Marcelo,
Raizada Mohan K
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1237.8
Subject(s) - minocycline , microglia , neuroinflammation , endocrinology , medicine , hypothalamus , premovement neuronal activity , downregulation and upregulation , immunostaining , chemistry , inflammation , neuroscience , biology , immunohistochemistry , biochemistry , gene , antibiotics
Objective Our studies have previously established that neurogenic hypertension is associated with microglial activation in cardioregulatory brain centers, such as the paraventricular nucleus of the hypothalamus (PVN). Treatment with minocycline, an inhibitor of microglial activation, attenuates the persistent increase in blood pressure, peripheral and central inflammation, as well as autonomic dysfunction in vivo . In the present study, we tested the hypothesis that microglia play an important role in modulating Ang II induced neuronal activity and neuroinflammation. Methods Adult Sprague Dawley (SD) rats were infused with SQ saline or Ang II (200ng/kg/min) and treated with oral vehicle or minocycline (50mg/kg). Manganese‐enhanced magnetic resonance imaging (MEMRI) was performed at 4 weeks of infusion to indirectly visualize neuronal activity across cardioregulatory brain networks. After imaging, brains were isolated for microglia Iba1 immunostaining to establish potential mechanisms underlying altered brain activity. Primary neuronal and mixed neuroglia cultures were prepared from SD pups on day E20–21. Cultures were treated with 20μM minocycline for 1 hour followed by 1μM Ang II for 6 hours on day 5 for mixed cultures or day 10 for primary neuronal cultures. Results Under control conditions, MEMRI detected basal activation of the PVN. In rats infused with Ang II, there was a marked increase in manganese accumulation in the PVN, which is likely indicative of increased PVN neural activity; this effect was markedly reduced by the minocycline treatment, an effect associated with decreased microglial activation in the PVN. In vitro, Ang II induced a 40% upregulation of c‐fos in mixed culture (p<0.01), indicative of neural activation, which was effectively blocked by minocycline pretreatment. Additionally, Ang II increased pro‐inflammatory genes mRNA in vitro , including Il1b (1.5‐fold, p<0.001), Tnf (1.4‐fold, p<0.05), Ccl2 (1.2‐fold, p<0.01), and Nos2 (1.8‐fold, p<0.01), indicative of M1 microglial polarization. Minocycline pretreatment was able to reverse these effects in mixed neuroglia cultures. However, in primary neuronal cultures, minocycline only decreased Nos2 (p<0.05), and did not affect c‐fos or pro‐inflammatory gene expression. Conclusion These data indicate microglia activation plays an important role in modulating Ang II induced neuronal activity and neuroinflammation in PVN. Furthermore, minocycline indirectly modulates neuronal activity in vivo and in vitro by inhibiting microglial activation. Support or Funding Information HL 33610 (MKR)