The Role Of RNA Binding Protein Qki In Macrophages Polarizations And Its Anti-inflammatory Mechanisms In Against Infection

Sepsis is a systemic inflammation caused by infections with pathogens such as bacteria or viruses,with organ damage,failure,and even death.Because of its complex pathogenesis,traditional methods such as antibiotics and fluid therapy have limitations,and sepsis mortality rate remains high.It is of great theoretical value and clinical significance to explore the pathogenesis of sepsis and pursue new therapeutic strategies.When infected by pathogens,macrophages,as guardians of the body's innate immune system and are able to pathogens by phagocytosis,killing,and secreting cytokines.Macrophages are plastic and polarized into two distinct subpopulations in the immune microenvironment including: pro-inflammatory M1 subtype and anti-inflammatory M2 one.In the early stages of inflammation,M1 mainly plays a pro-inflammatory function by recruiting and activating adaptive immune cells,via secreting various cytokines such as IL-6 and TNF-?.Later on,macrophages switch to M2 type,secreting IL-10 and TGF-?,and promotes tissue repair and wound healing.The homeostasis of immune response is precisely controlled by macrophage subtype transition causes a transition from an inflammatory phase to an ablation phase that is precisely controlled.The aberrant status of macrophages polarization is the leading cause of lethality in sepsis.Therefore,understanding signaling pathways in the regulation of polarized macrophages will be helpful for the sepsis treatment.However,the molecular mechanism of macrophage polarization has not yet been fully revealed.The RNA-binding protein QKI(quaking)directly regulates RNA metabolisms by participating in the process of RNA splicing,stability and translation.We previously discovered that QKI is involved in the regulation of mononucyte-macrophage differentiation.To further elucidate whether QKI is involved in the regulation of macrophage polarization,we conducted a series of experiments at the cellular and animal level.Our findings are in the following points:1)The relevance of QKI expression is related to the polarization subtype of macrophages.By constructing the macrophage polarization model in vitro,we found that QKI expression was decreased in Ml macrophages.In contrast,QKI expression increased under M2 induction conditions.2)The functions of QKI in favoring M2 polarization against M1 status.We set up a stable transfectant cell lines RAW264.7 cells with either QKI interference or overexpression.We have found that QKI is involved in regulating the polarization of macrophages.Under M1 polarization conditions,the expression of M1-associated pro-inflammatory markers iNOS,TNF-? and IL-6 in QKI-silenced macrophages was significantly up-regulated,whereas anti-inflammatory factors such as IL-10,Fizz1,Chil3 or Ym1 were decreased.Interestingly,even under M1 induction conditions,overexpression of QKI promotes the down-regulation of M1 type pro-inflammatory cytokines in macrophages,while M2 type marker molecules up-regulate expression.3)Mechanism study found that QKI upregulated Aryl hydrocarbon receptor(Ahr)expression and phosphorylation of signal transducer and activator of transcription 1(STAT1),thereby inhibiting NF-?B transcriptional activity.In addition,QKI also inhibit the activation of NLRP3 inflammasomes,which in turn inhibit the secretion of IL-1?,and this process also depends on Ahr.In vivo construction of an LPS-induced mouse sepsis model revealed mortality in myeloid specific knockout QKI mice(100%,p < 0.01)and serum pro-inflammatory factors level(TNF-?,IL-6,IL-1?)was significantly higher than that in the control group;conversely,transferring QKI-expressing macrophages into myeloid-specific knockout QKI mice improved survival in mice,and the mouse pro-inflammatory cytokines IL-6,TNF-? and IL-1? were significantly down-regulated,whereas IL-10 levels were elevated and the proportion of M2 macrophages is increased.In conclusion,our study demonstrated that QKI regulates macrophage polarization through the Ahr/STAT1-NF-?B pathway,inhibiting excessive inflammatory responses in sepsis.This study revealed a new mechanism of macrophage polarization,expanding the biological function of QKI,and providing a theoretical basis and experimental basis for the development of sepsis therapeutic drugs using QKI as a potential target.