The use of siRNA as a pharmacological tool to assess a role for the transcription factor NF-IL6 in the brain under in vitro and in vivo conditions during LPS-induced inflammatory stimulation.

BACKGROUND: Studies with NF-IL6-deficient mice indicate that this transcription factor plays a dual role during systemic inflammation with pro- and anti-inflammatory capacities. Here, we aimed to characterize the role of NF-IL6 specifically within the brain.

METHODS: In this study, we tested the capacity of short interfering (si) RNA to silence the inflammatory transcription factor nuclear factor-interleukin 6 (NF-IL6) in brain cells under in vitro and in vivo conditions.

RESULTS: In cells of a mixed neuronal and glial primary culture from the rat area postrema (AP), short interfering RNA (siRNA) directed against NF-IL6 strongly reduced basal and lipopolysaccharide (LPS)-induced nuclear immunoreactivity of this transcription factor, with the strongest effect on astrocytes. The siRNA did not exert inflammatory effects in the primary culture as confirmed by unaltered levels of IL-6 in supernatants. In vivo, intracerebroventricular (i.c.v.) injections of fluorochrome labelled siRNA caused its appearance in relevant brain structures for fever induction pathways such as the vascular organ of lamina terminalis, the subfornical organ, the median preoptic nucleus (MnPO) and the AP in several cell types, including microglial cells. However, i.c.v. injections of siRNA per se caused signs of fever, anorexia and reduced locomotor activity, i.e. sickness behavior.

CONCLUSIONS: This approach was, thus, not suitable to characterize the role NF-IL6 in the brain in vivo, namely during experimentally induced systemic inflammation.