Interleukin-6 (IL-6) receptor/IL-6 fusion protein (Hyper IL-6) effects on the neonatal mouse brain: possible role for IL-6 trans-signaling in brain development and functional neurobehavioral outcomes

Adverse neurodevelopmental outcomes are linked to perinatal production of inflammatory mediators, including interleukin 6 (IL-6). While a pivotal role for maternal elevation in IL-6 has been established in determining neurobehavioral outcomes in the offspring and considered the primary target mediating the fetal inflammatory response, questions remain as to the specific actions of IL-6 on the developing brain. CD-1 male mice received a subdural injection of the bioactive fusion protein, hyper IL-6 (HIL-6) on postnatal-day (PND)4 and assessed from preweaning until adulthood. Immunohistochemical evaluation of astrocytes and microglia and mRNA levels for pro-inflammatory cytokines and host response genes indicated no evidence of an acute neuroinflammatory injury response. HIL-6 accelerated motor development and increased reactivity to stimulation and number of entries in a light/dark chamber, decreased ability to learn to withhold a response in passive avoidance, and effected deficits in social novelty behavior. No changes were observed in motor activity, pre-pulse startle inhibition, or learning and memory in the Morris water maze or radial arm maze, as have been reported for models of more severe developmental neuroinflammation. In young animals, mRNA levels for MBP and PLP/DM20 decreased and less complexity of MBP processes in the cortex was evident by immunohistochemistry. The non-hydroxy cerebroside fraction of cerebral lipids was increased. These results provide evidence for selective effects of IL-6 signaling, particularly trans-signaling, in the developing brain in the absence of a general neuroinflammatory response. These data contribute to our further understanding of the multiple aspects of IL-6 signaling in the developing brain.

Both Th1- and Th2-derived cytokines in serum are elevated in Graves' ophthalmopathy

Increased serum cytokine levels have been reported in patients with autoimmune thyroid disease, but less is known about their levels in patients with Graves' ophthalmopathy (GO). It is not known whether GO is a cell-mediated or humoral autoimmune disease. We investigated whether serum cytokines are elevated in GO patients and whether the cytokines were Th1- or Th2-derived. In addition, elevated cytokines might reflect the activity of GO, and thus we investigated whether cytokine levels could predict the clinical response to orbital radiotherapy. We studied 62 consecutive patients with moderately severe untreated GO and 62 healthy controls, matched for sex, age and smoking habits. Serum concentrations of IL-1RA, sIL-2R, IL-6, sIL-6R, tumour necrosis factor-alpha (TNF-alpha) RI and II and sCD30 were measured using highly sensitive ELISAs, in the patients before and 3 and 6 months after radiotherapy. All patients were euthyroid, with anti-thyroid drugs, before and during the entire study period. All baseline cytokine and cytokine receptor levels were significantly elevated in GO patients compared with healthy controls, except for IL-1RA. The levels did not correlate with parameters of the thyroid disease, nor with the duration, activity or severity of GO. However, backward logistic regression analysis showed that IL-6, sCD30 and TNFalphaRI were able to predict a beneficial response to orbital radiotherapy. We therefore conclude that both Th1- and Th2-derived cytokines are elevated in GO patients compared with its controls. IL-6, sCD30 and TNFalphaRI had some value for predicting therapeutic outcome to orbital irradiation, and may thus reflect active eye disease.