miR-146a and Astrocyte Inflammatory Response Figure 4. miR-146a expression levels after transfection with anti-miR-146a LNA or miR-146a mimic (pre-miR146a). Quantitative real- time PCR of miR-146a. (A) miR-146a expression after transfection with LNA-antimiR-146a (50 nM) in U373 cells; insert shows in green tranfected cells (B) miR-146a expression after transfection of miR-146a mimic (pre-mir-146a, 1, 25 and 50 nM). (C) miR-146a expression 24 hours after exposure to IL- 1b in U373 cells transfected with LNA-antimiR-146a (50 nM) or miR-146a mimic (pre-mir-146a, 50 nM). (D) miR-146a expression 24 hours after exposure to IL-1b in cultured human astrocytes transfected with LNA-antimiR-146a (50 nM) or miR-146a mimic (pre-mir-146a, 50 nM). Data are expressed relative to the levels in unstimulated cells and are mean 6 SEM from two separate experiments performed in triplicate (*p,0.05 compared to control; **p,0.05 LNA or mimic transfected cells stimulated with IL-1b, compared to IL-1b alone). doi:10.1371/journal.pone.0044789.g004 levels of IL-6, IL-8, G-CSF, IFN-c, IP-10, MIP-1b, and TNF- a (Fig. 8). intractable epilepsy and provide evidence for a role of miR-146a in the regulation of the astroglia mediated inflammatory response. Discussion The miR-146a has recently been shown to be upregulated in experimental models of epilepsy, as well as in human TLE. [20,21]. In a rat model of TLE strong upregulation was detected in astrocytes 1 week after status epilepticus (during epileptogenesis) which corresponds to the latent period and the time of maximal astroglial activation and upregulation of various genes involved in the immune response [37,38]. These observations are in line with other studies supporting the association between this specific miRNA and human inflammatory diseases [15,16]. In particular, upregulation of miR146a has been detected in active multiple sclerosis lesions [39] and in human Alzheimer disease (AD) brain [19], suggesting a key role of this miRNA in governing astrocyte activation and function in both pathologies. However, there is still little information regarding miR-146a function in astrocytes, in particular regarding the effect on astroglia mediated inflammatory pathways in relation to epilepsy. In the present study, we demonstrate the overexpression of miR-146a in glioneuronal lesions from patients with medically MiR-146a Expression in GG and FCD IIB GG and FCD type IIb represent a major cause of drug-resistant epilepsy [23,25] and are characterized by a prominent activation of various inflammatory pathways, including the TIR signaling pathway [9,40–43]. In the present study, we provide evidence for upregulation of miR-146a in these epilepsy-associated glioneur- onal lesions. Increased levels of miR-146a were detected GG and FCD type IIb compared to both control autopsy material and histologically normal surgical cortex (without alteration in cortical lamination or astrogliosis) from patients with epilepsy. The latter excludes the direct effect of recurrent seizures and antiepileptic drugs on the detected expression level of miR-146a in FCD specimens. Thus seizures alone may not account for changes in miR-146a expression. The absence of differences in miR-146a expression between autopsy and surgical specimens excludes the possibility that this is an artefact of autopsy delay. Moreover, recent studies indicate a robust stability of miRNAs, supporting the accuracy of miRNA measurements with RT-qPCR [44]. In situ hybridization confirmed the increased expression of miR-146a in reactive astrocytes which are abundantly present within the PLOS ONE | www.plosone.org 8 September 2012 | Volume 7 | Issue 9 | e44789