Sleep enhances IL-6 trans-signaling in humans

Sleep is commonly considered to support immune defense. The underlying sleep-immune interaction appears to rely critically on cytokines, like interleukin-6 (IL-6), that combine effects on immune and neuronal functions. The IL-6 signal is conveyed in two ways: it stimulates a restricted group of (mostly immune) cells via membrane-bound IL-6 receptors (mIL-6R) by forming a complex with soluble IL-6R (sIL-6R), and it stimulates (via membrane-bound gp130) a great variety of other cell types--a process termed trans-signaling. Focusing on the receptor side of IL-6 signaling, we examined the effect of sleep on sIL-6R plasma concentrations, mIL-6R expression, plasma sgp130, and numbers of IL-6-producing monocytes in healthy humans who were tested during a regular sleep-wake cycle and 24 h of wakefulness while blood was sampled repeatedly. Sleep strongly enhanced concentrations of sIL-6R, exceeding wake levels by 70% at the end of sleep. This rise was due to an increase in the PC (proteolytic cleavage) rather than the DS (differentially spliced) variant of sIL-6R. Sleep did not affect IL-6-producing monocytes, mIL-6R density, or sgp130 concentrations. The selective increase in sIL-6R implicates an enhanced trans-signaling capacity whereby sleep distinctly widens the profile of IL-6 actions, enabling an integrated influence on brain and peripheral organs

Transgenic blockade of interleukin 6 transsignaling abrogates inflammation

The immunoregulatory cytokine Interleukin-6 (IL6) acts in a pro- and anti-inflammatory fashion. Synthesized by myeloid cells, fibroblasts and endothelial cells, IL6 on target cells, binds to the IL6 receptor (IL6R) and signals via complex formation with the ubiquitously expressed gp130 receptor. Paradoxically, most cells, which respond to IL6 during inflammatory states do not express the IL6R and are themselves not directly responsive to the cytokine. A naturally occurring soluble form of the IL6R renders all cells responsive to IL6. This alternative signaling process is called IL6-trans-signaling. Here we developed a transgenic strategy based on the overexpression of the soluble form of gp130, which specifically blocks all IL6 responses mediated by the soluble IL6R but does not affect IL6 responses via the membrane bound IL6R. In these mice, inflammatory processes are blocked as in IL6-/- mice strongly arguing for a major role of the soluble IL6R during inflammation in vivo

Therapeutic targeting of IL-6 trans signaling counteracts STAT3 control of experimental inflammatory arthritis

Cytokine control of the synovial infiltrate is a central process in the development of inflammatory arthritis. In this study, we combine genetic approaches and intervention strategies to describe a fundamental requirement for IL-6-mediated STAT3 signaling in orchestrating the inflammatory infiltrate in monoarticular and systemic models of experimental arthritis. STAT3 activation via the common gp130 signal-transducing receptor for all IL-6-related cytokines led to increased retention of neutrophils and T cells within the inflamed synovium, which included STAT3-regulated IL-17A-secreting T cells. Control of leukocyte infiltration was reliant upon IL-6 signaling via its soluble receptor (termed IL-6 trans signaling), as evidenced by selective blockade of this alternative IL-6 signaling pathway using an engineered variant of soluble gp130 (sgp130Fc). This therapeutic intervention led to substantial clinical improvement in mice with emerging or established incidence of systemic arthritis. These data illustrate that IL-6 control of STAT3 is critical for regulating the synovial infiltrate in inflammatory arthritis, and suggest that selective inhibition of IL-6 trans signaling may provide a more refined intervention strategy for blocking IL-6-driven proarthritic activities

A human ortholog of archaeal DNA repair protein Hef is defective in Fanconi anemia complementation group M

Fanconi anemia (FA) is a genetic disease featuring genomic instability and cancer predisposition1. Nine FA genes have been identified, and their products participate in a DNA damage response network involving BRCA1 and BRCA22,3. We have previously purified a FA core complex containing the FANCL ubiquitin ligase and 6 other FA proteins4–6. Each protein in this complex is essential for monoubiquitination of FANCD2, a key reaction in the FA DNA damage response pathway2,7. Here we show that another component of this complex, FAAP250, is mutated in FA patients of a new complementation group (FA-M). FAAP250, renamed FANCM, has sequence similarity to known DNA repair proteins, including archaeal Hef, yeast Mph1 and human ERCC4/XPF. FANCM can dissociate DNA triplex, possibly due to its ability to translocate on duplex DNA. FANCM is essential for FANCD2 monoubiquitination and becomes hyperphosphorylated in response to DNA damage. Our data suggest an evolutionary link between FA proteins and DNA repair; FANCM may act as an engine that translocates the FA core complex along DNA