Chronic low-grade inflammation contributes to the pathology and complications of type 2 diabetes (T2D). Interleukin-10 (IL10), an anti-inflammatory cytokine, is suggested to play a protective role in T2D. However, the impact of T2D on IL10 function has not been previously assessed. We examined the ability of IL10 to inhibit inflammation in human T2D immune cells and explored underlying mechanisms using macrophage models. IL10 was less effective at inhibiting tumour necrosis factor (TNF)-α secretion in T2D whole blood cultures, which was not explained by altered IL10 receptor surface expression. These findings were observed in macrophages exposed to high glucose, which demonstrated similar IL10 resistance or hyporesponsiveness. These findings were also not explained by changes in IL10 receptor protein or other downstream signaling proteins. High glucose was also shown to impair the ability of IL10 to activate STAT3, a downstream signaling protein of IL10. Treatment with the SHIP1 agonist, AQX-MN100, reversed IL10 hyporesponsiveness in macrophages cultured in high glucose and showed equal effectiveness at different glucose conditions. This data supports the idea that IL10 hyporesponsiveness may contribute to chronic inflammation in T2D. These novel findings suggest that strategies aimed to overcome IL10 hyporesponsiveness may hold therapeutic potential for reducing inflammation in T2D.

Summary The anti-inflammatory actions of interleukin-10 (IL10) are thought to be mediated primarily by the STAT3 transcription factor, but pro-inflammatory cytokines such as interleukin-6 (IL6) also act through STAT3. We now report that IL10, but not IL6 signaling, induces formation of a complex between STAT3 and the inositol polyphosphate-5-phosphatase SHIP1 in macrophages. Both SHIP1 and STAT3 translocate to the nucleus in macrophages. Remarkably, sesquiterpenes of the Pelorol family, which we previously described as allosteric activators of SHIP1 phosphatase activity, could induce SHIP1/STAT3 complex formation in cells and mimic the anti-inflammatory action of IL10 in a mouse model of colitis. Using crystallography and docking studies we identified a drug-binding pocket in SHIP1. Our studies reveal new mechanisms of action for both STAT3 and SHIP1 and provide a rationale for use of allosteric SHIP1-activating compounds, which mimic the beneficial anti-inflammatory actions of IL10. Video Abstract

Transfection of desired genetic materials into cells is an inevitable procedure in biomedical research studies. While numerous methods have been described, certain types of cells are resistant to many of these methods and yield low transfection efficiency 1 , potentially hindering research in those cell types. In this protocol, we present an optimized transfection procedure to introduce luciferase reporter genes as a plasmid DNA into the RAW264.7 macrophage cell line. Two different types of transfection reagents (lipid-based and polyamine-based) are described, and important notes are given throughout the protocol to ensure that the RAW264.7 cells are minimally altered by the transfection procedure and any experimental data obtained are the direct results of the experimental treatment. While transfection efficiency may not be higher compared to other transfection methods, the described procedure is robust enough for detecting luciferase signal in RAW264.7 without changing the physiological response of the cells to stimuli. Video LinkThe video component of this article can be found at